How to DEBUG Pine Script Code

g'day Traders welcome back to another video on our favorite language Pine script in today's video we're going to be dealing with a subject that's not particularly sexy but it is very important for us to understand and that is the subject of debugging our scripts for those who aren't aware of the term debugging it basically just means looking under the hood of our script and seeing what the script is actually doing for example if we're working with the for Loop and our script is giving us incorrect output then we may want to look inside the for Loop and see what each Loop is doing and that's what I have on my chart here we have two labels here that is essentially debugging a for Loop now there are multiple ways to debug our scripts there are multiple reasons why we might want to and in today's lesson we're going to cover all of those but before we do that I just want to really quickly make you guys aware of our free Weekly Newsletter that I send out every Wednesday where I share a 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the email newsletter if that's something you're interested in with that out of the way let's get into today's lesson alright so to get started here I just have a simple script that's plotting the closing price of the market that we're on Market is irrelevant but we're on bitcoin for now and we're planning a horizontal line at twenty thousand this is just to set the chart scale and I'll explain why in a moment so open up my code here we're just plotting the closing in price and we're giving the plot a title you could also specify this but if you're not aware in Pine script you need to put the parameters in order of their appearance in the documentation so the first thing we're plotting is a series in this case it's the closing price series the second parameter is a title so I can have a string Title Here the third parameter is a color so if I put them in order I don't need to specify what the parameter is but if they're not in order like this then the script won't compile because these parameters are not in the correct position and so what I would need to do here if I wanted to put the parameters in any order I need to specify what the parameters are so we have a plot here that's plotting the closing price color of blue and the title closing price so now if I come up to the data window which is this button here and I click on that here is the date and time of the market we're on here is the markets price data volume and open high low close and then here is our script that we've added to the Chart so this data window will list all of the indicators you have added to your chart and when we're developing a script this is where we can start to debug our values so if I hover my mouse over past bars here you'll see this closing price data value updating so this is the first introduction to debugging your scripts obviously you can also just look at the plot here but if you've got several plots drawing out on your indicator it can get really confusing knowing which one's which so that's where the data window comes in handy we can see the title of each value that we're drawing so now that we have our chart scale set let's create some debugging values some values we can work with so for today's video I'm going to just work with volume average volume so what we're doing here is we're getting the average volume over the past 50 bars using an SMA simple moving average or smooth moving average so we're calculating the 50 period SMA of volume and that gives us our average volume then we have a Boolean value here true false value that checks if the current bars volume is greater than the average volume over the past 50 bars so now if we wanted to debug the raised volume Boolean value and see if it's true or false on each bar in our chart we can use the plot function for this however if I just try to plot raised volume as a plot like this my script won't compile because this is a Boolean value not a number and plot can only plot numbers so what we would need to do here instead is use a conditional operator so we can say is raised volume true question mark If so plot one otherwise plot zero now when I save my script we'll be getting ones and zeros drawing up here to let us know whether or not volume is raised above the moving average I can also title this uh raised volume and now this plot is showing up in my data window however if I minimize this script you can see that our chart scaling is now all screwed up so we're plotting 0 and 1 all the way down here we're also plotting the price value and because we're plotting one or zero the chart will automatically scale to show all the plots in your script and so that screws up our our chart scaling the way we can get around this and still plot this one and zero debug value to the data window is using the plot cha functional car plot character this is short for plot character to the chart and it's similar to the plot function in that it takes a series however it also takes a character and so what we can do here is I can just get rid of title since we're inputting all these parameters in order I can plot our series our title the character is just going to be blank and we can leave it as that and if I save my code the chart scale here will be corrected see now it is um automatically scaling because I'm on auto here if you look really closely it's hard to see but there's these little blue dots all over the place those are our plot character functions plotting a blank character I don't know why it plots a DOT instead of a blank character which is what we wanted but it's an easy thing to fix all we need to do is specify the color of our plot chart function and it doesn't matter what color you set this to because we're going to set the colors transparency to 100 so I could set this to color dot new color.red 100 and now what you'll see is this number here will turn red and all of those little blue dots on my chart will disappear so keep an eye on these two things there we go our raised volume is now red and we are not getting anything drawing out of the chart you can do the same thing with regular plots but again remember that will screw up your chart scaling in many circumstances so that's one way to debug Boolean values another way my preferred method when I'm developing a script just because it's really quick and easy and very I'm a very visual Trader so just staring at a bunch of numbers will often just make my brain switch off so I like to use things like changing the background color of my chart based on a condition when I'm developing my script once I've built my script maybe I'll change that background color into a plot shape something that looks a little bit better a little bit more tidy but when I'm developing and I want to get my code written quickly I'll just use the BG color function to check is raised volume true if so set the background color of my chart to color dot green with 50 transparency otherwise set my background color to nothing now if I save my code I can close the data window and I can just see when volume is raised by this background color here now it looks terrible obviously so when you finish your script as I said you might want to turn this into a plot shape function that draws boxes at the bottom of your indicator or something like that but for now this will do it's a very quick method for debugging particularly market conditions and just general true false values so that's the beginning of debugging now the next thing I was going to show you which I already have shown you is the plot Char difference so let me copy some code over here and explain what's happening displaying data in the data window is achieved using plots so plots do work plot shapes also work that will sharpen the in the data window however the preferred option is plot sha as I mentioned because it will not affect your chart scale so now if I saved my code we won't be drawing raise volume anymore but now we're plotting out average volume so we can actually see what our average volume is and if I copy this code and paste underneath here volume and I can say current volume now we can compare the average volume to the current volume and so if you look at when I hover over a green bar current volume is going to be higher than average volume that's the condition that sets our background color of our chart to Green but just to reiterate for those who are new to Pine script if I were to plot the number one onto my chart that's going to jack up my chart scaling because now we're plotting one all the way up to the current market price which is 22 000. so the correct method is to use plot chart so that covers the majority of circumstances where you might want to debug your script obviously this is a super simple script but if you're working with dozens of different values you can use a plot chart function to see what they're all doing and sort of break down the inner workings of your script and C under the hood see what all of your variables are by hovering over each bar on your chart and you can double check and confirm that your script is doing what you think it's doing however when we're working with for Loops things get a little bit more complicated because if I write out a simple for Loop here we can't say plot chart the current bars volume in our for Loop uh let's say volume with a blank character if I save my code here we're going to get an error because we cannot use any plot functions inside a local scope so that means we cannot use it in an if statement anything that's tabbed this is a local scope of our for Loop we cannot use any plots anything to draw to the Chart inside a scope so we can't draw in for Loops we can't draw an if statements we can't draw in functions we can only draw in the main scope of our script so if we want to see what our for Loop is doing on each Loop things are a little bit more complicated for today's example to keep things really simple let's just add up the bar size of the past 10 bars technically this would be the past 11 bars because we're starting from zero counting up to 10. if we wanted to do the past 10 bars this would be 0 to 9 and that would start counting from the current bar 0 back 0 1 2 3 4 5 6 7 8 9 which would be ten bars so I'll leave it as that for now let's count back the past 10 bars and what we're going to do is we're going to add up the total bar size over that look back period to do that I just need to add or update the total bar size to whatever its current value is on its on this current Loop plus the current bars High the current bar in our Loop so I is the bar index of our Loop so the high minus the low of this current Loop and then I can use a plot Char to plot what our total bar size is so now if I save my code this is incorrect let me change that to Total bar size so now we can see that the total bar size adding up the bar size of the past 10 bars on our chart gives us 2632 and now if I were to divide this number by 10 that would give us the average bar size over the past 10 bars let's do that next I can say average bar size equals total bar size divided by 10. now if I wanted to turn this into a user input I could say a loop length equals input dot integer look back I will give it a default value of 10 and I I've been getting into a new habit of declaring what my data type is when I declare a variable you don't have to do this Pine script will automatically detect what type of what data type you're working with but I've started to do this because with the new latest Pine editor the color coding it makes it a lot easier to read your code and see what each variable is so anyway here's our Loop length When We're looping remember zero counts as one so what we need to do here is subtract one from our look back length and then when I'm dividing my average bar size I need to paste that Loop length in there without subtracting one from it and now we're looping from zero to nine technically 10 bars and then dividing the total bar size by our look back length now if I save my code well actually I forgot to plot this hang on um let's plot the average bar size I'll put this under our bar size I think that'll make it more intuitive to read the data window so now when my script compiles we have the total bar size of the past 10 bars and we have the average bar size over those 10 bars and if I wanted to I could also add in our look back length and paste that in there and so now all these red numbers are showing us our look back period total bar size over that look back period and the average bar size over that look back period however what if we were doing something more complicated within this for Loop and our script was giving incorrect output and we didn't know why that's where debugging the for Loop comes into play and the best way to do this there are multiple ways you could create an array and you could feed each value into into the array and plot them all individually using plot charts that's an option but it's a little bit convoluted my preferred option is to Simply do what's referred to as building a string so we can build a string a string of text that adds the for Loop values to the text and then at the end of our for Loop we can draw a label onto our chart that shows what happened within the for Loop during each Loop so to do that I'm going to create a new variable here called string debug string and it's going to start out as just a blank string with nothing in it and then what we're going to do is we're going to build our string so the same way we add up our total bar size by assigning total bar size 2 total bar size plus the latest Loop value we do the same thing with our debug string so we're going to set debug string to whatever it currently is plus and then I'm going to this is going to get a little bit complicated to read but it's really quite simple what we're going to do here is we're going to open a square bracket and then add the current Loop index I to this string so that we know what this string is referring to but remember when we're dealing with pinescript we cannot add a number to a string directly we need to use these Str dot to string function to convert the number into text so that our script will compile and now if I close that bracket off and I add a backslash n this backslash n will create a new line and then when we draw this string onto a label each Loop value will be on its own line and will make it easier to read so now that we have our debug string we'll expand on this in a moment but just so that we are all on the same page let's first simply draw this debug string to the chart using a label so to do that I'm going to check if the current bar state is the last bar on my chart if I don't do this and we just draw a label on every bar then we'll have labels all over the place and it will be really hard to read so what we want to do is only draw the label on the final bar and then we can debug the latest 10 bars to make sure that our script is doing what we hope it is so to create a new label I can say label.new and then we need to pass in the bar index and a price value so for this label I'll set it to the current bars high now we need to specify the text for the label that's just going to be our debug string and I'm also going to set the color to color.black and the text color to colored hot white and one final thing I'm going to do to make our label easy to read is set the text align to left because I think by default it's centered and so if we have an inconsistent string length it'll Center everything and it's just not ideal we want everything to be aligned to the left that'll make it easy to read so I can set text align equals text Dot align left and let's hide the data window so we can see more code here so now when I save my code keep an eye on this label here there we have it so we are now building a string and each string starts with the loop index and then what we can do here is we can start adding values from within our Loop so for example we could say here total bar size equals plus str.2 string total bar size and then I need to finish that string and now let's save my code we'll be getting more information on this label there we go so on the very first loop on the very first bar in our chart the total bar size is 155 and we can verify that by measuring the bar and close enough 155 so this is an accurate value then we can check Loop number one which is this next bar back the bar size there is 312 so now if I measure from the high down to the low 155 plus 169 is approximately 312. so remember we're adding up the bar sizes as we loop back if we wanted to see what the bar size of each bar is on our Loop we need to change our code a little bit here and to make this easier to read this isn't necessary you can just keep writing the string off the screen if you want to but since I'm doing this for YouTube I'm going to start a new line here and to start a new line when you're dealing with a single expression in Pine script this here is an expression if I want to extend this expression to multiple lines then I need to press enter here then tab and then one space I don't know why but that's how bindscript works if I don't have the space here my script will not compile but if I add a space after that tab it will compile I think you can also just have one space here that works too so whatever makes more sense to you personally I find the tab in one space makes more sense to me because it's more obvious that I'm extending this line um sometimes it might be hard to see this single space but it's just a matter of preference just make sure that you have one space after you start your new line and you're at least on the same scope as our expression so now what I can do is I'll actually bring this one back and we'll start a new string here we need to have a space here because otherwise this will add on to the end of this number so one space and then I can say bar size equals and then str.to string High minus low of our current Loop and then now if I save my code we should be getting more information so now it's showing the bar size of each bar as we loop back and it's showing the total bar size as that is being accumulated so you can see now how this can really help us get an insight into what our for Loops are doing and that's really it I mean we could add more information here if we want to so for example I could start a third line here and I could specify or display the current bars high price and the current bars low price and when I say current bar I mean the current bar in our Loop so when I save my code now we're getting a lot more information we're getting the total bar size the current bar size the current bar is high the current bar is low and the corresponding Loop index for that information and so now we can double check that our script is actually working with the same data that we want it to and it's outputting the correct information and that's it that's really it for PostScript debugging unfortunately there's no better way to do this sort of thing I wish the data window had an option for plotting things that do not draw onto your indicator values any plots even plot charts that are blank and aren't drawn onto your indicator will have a number here in the indicator values list I wish there was a way to hide these so that you could only see them in the data window that would make some scripts a lot tidier especially ones that have tons of plots like my ultimate pullback indicator that I showed you guys in the previous video that has tons of plots and these numbers just go off the chart and it just clutters up your screen obviously you can come into the settings menu and you can turn off indicator values and then they're all gone but sometimes you want to know what those indicator values are without opening the data window but anyway I digress I also wish there was a way to send text directly to the console here that would make things so much easier for us as Pine scripters if we could just say print and then some sort of text and that would come into the console that would be a super useful feature in panscript but unfortunately for whatever reason we do not have that capability yet and so the next best thing is just using labels and so before I wrap up this lesson let's first of all set overly to True here and I will remove this script and add it back to my chart so that we're drawing over actual price action and the final thing I want to show you guys is how to debug a specific bar so this is debugging the latest bar the last bar on our chart but what if we wanted to go back around here somewhere and analyze this bar here well there is one method for doing this that is pretty convenient and that is using a user input that sets a bar time and then if you set that user input to confirm I'll show you what that means in a moment if confirm is true on that user input then you can click on the bar itself and tell your script where to start drawing something like a label so to wrap up this lesson let me show you how to do this I'll just paste over some code to save time so this time we're using a confirm time input to display a label on the selected bar so we're getting an integer bar time which is a Unix timestamp you don't need to know what that means but it's basically just a timestamp it allows you to specify a time as an integer simple integer that will tell our script where we want to draw something so in this case we're using the input.time function the default value will be negative one and we have set confirm equals true and what this will mean is when we add the script to our chart for the first time we will need to use our Mouse to select a bar so now I can pretty much copy this line of code here to check if we're on the last bar on our chart and then I can say and bar time is not equal to negative one that means that the user has selected a bar time if a user has selected a bar time then we want to draw our label on the selected bar so to do that we just need to change our bar index to Bar time however we also need to inform or tell the label function that we are working with bar time and not a bar index so by default the label function the x value the first value in this label function is a bar index so the very first bar in our chart will be bar index 0 and then the latest bar on our chart will be however many bars are drawing on our chart in this case we don't want to use bar indexes or indices we want to use bar time so to do that I need to tell my label function that the X lock value is supposed to be X locked up bar time instead of bar index so we're overwriting the default value for x-lock from bar index to Bar time we're getting the bar time as a user input the user must select the bar with their Mouse and then if we're on the final bar on our chart and the user has selected a bar time then we'll draw a new label on that bar you can save my code here now nothing's going to change because we've already added this script to our chart so when I come up to the settings menu and go to input the select bar input is going to be set to the default value which is 1917 first of January 1970 which is when the Unix timestamp begins calculating from it again that's not information you need to know about what you do need to know is that if you want to be able to just select a bar without coming in here and setting your gear and date and time and all of that which is annoying and clunky what we want to do is remove our script from our chart and then add it back onto the chart and now you'll see this pop-up select the select bar time for this script so my script is named after my website but here would be your script title and now you'll see that my script has a vertical line and whichever bar I click on will be the bar that we draw our label on so you can hold Ctrl or command on a Mac to tell pan script where you want to zoom in so if I hold down control and I go all the way back let's do a bar in here let's do this uh this top bar here when I click on this bar like so we are getting a label drawing now the label is all the way down here I'm not exactly sure why that's happening it should be drawing on the bars high so maybe I need to specify my y lock value here while lock Dot above bar let's try that save my code there we go that's better so now the label is drawing above the bar that I selected which was this swing High bar here and we're getting our for Loop data drawing into a label over the past 10 bars starting from this bar and we can do our debugging across those bars to make sure and confirm that all of these values here are accurate I should mention that you can also debug custom functions as well in order to do that this is a custom function defined the very last line in your function is what the function returns and so if you wanted to debug what your custom function is doing you could do something like this test two and test one so test one is going to be a local variable created within our custom function and it's going to be set to this value that's inputted into our custom function times 2.5 and then Test 2 is going to be this same value times 4 and now if I create a new value here called custom func is set to FN let's set it to one that way we can very easily see that this value is 2.5 and this value is 4. and now if I plot char our custom phone function value and I give it a title let's just title it custom function number one and I save my code and open the data window you'll notice that this number here is four so what's happening is our custom function is doing whatever it does here the executing this code and then the function outputs the final line of code here so whatever this final line of code is is the function's output so in this case that's test times four so what if we wanted to multiply test two by test one so test one multiplied by four let me save my code now keep an eye on this number that should be 2.5 times 4 which gives us 10 but what if we wanted to know what test one was inside of our function this is where things get a bit complicated those of you in the Mastery course will probably be more familiar with custom functions as we cover a whole module in there on this subject as well as what I'm about to show you which is tuples so if your head is spinning right now don't worry that's normal this stuff a bit complicated it takes a while to wrap your head around but basically what we need to do with our custom function is return two values to do that we use the square brackets and I can put test one and test two in here and now this line of code will not compile because we're returning a tuple this function is returning two values now so what we would need to do here is open some square brackets and we need to specify the two values from our function and now I actually need to get rid of this data type because Pine script will automatically detect what these two values should be and so our function is now outputting two values test one and test two and if I want to plot the first value that'll be this value here so custom fund one and if I paste this down here and change this to two and add to two save my code we'll now be getting two values down here the first one is test one which is going to be this value times 2.5 and the second value here is going to be test 2. which is test one multiplied by 4 which gives us 10. so hopefully that makes sense if it doesn't just re-watch this last part of the video a few times and eventually it will click so that'll do for today's video I'll leave the source code to this below a link to the source code below for those of you who want to dive into the code and actually play around with it yourself I know this lesson wasn't as exciting as some of our other lessons creating strategies and indicators and tools but this is an important subject that I get asked about pretty often and it's something we all need to be aware of as Pine scripters there will come times when your script is not doing what you want it to do and depending on the complexity of your script that can be a little difficult to pin down what's going wrong these are a few methods you can use to figure that out with all that said I'll leave this video here thanks for watching as always make sure to subscribe if you haven't already because I'll be back real soon with a new pan script video if you want to level up your plan scripting make sure to check out our courses at partnership mastery.com there's a free basis course there with several hours of content for those of you who are new to Pine script if this lesson went way over your head then you might want to start there but anyway thanks for watching I love you guys best of luck with your trading and I'll speak with you soon take care

Channel: The Art of Trading

Views: 11,907

Keywords: tradingview, pine script, tradingview indicators, forex algo, crypto algo, stock algo, trading algo, trading algorithm, how to create trading strategies, how to code your own trading scripts, trading scripts, forex scripts, crypto scripts, stock scripts, trading signals, forex signals, crypto signals, stock signals, detect trading setups, pine script mastery, pine script mastery course, how to use tradingview, how to use pine script, scripting, debug, debugging, troubleshoot

Id: b3PaVZkDbDI

Length: 30min 26sec (1826 seconds)

Published: Thu Feb 16 2023