Would like to add standard error bars to bar graph

I am having difficulty getting error bars to appear on my bar graph. For some reason, it graphs the means but not the standard error. I appreciate any constructive advice.

This is the graph I keep getting:

Here is the relevant code:

 AandBsumAex=find(AandB==1 & sess==0 & frAbase>=0);
 AandBsumA2ex=find(AandB==1 & sess==1 & frAbase>=0);
 
 FrAex=frAbase(AandBsumAex);
 FrBex=frBbase(AandBsumAex);
 FrA2ex=frAbase(AandBsumA2ex);
 FrB2ex=frBbase(AandBsumA2ex);

 M=[(mean(FrAex)),(mean(FrBex));(mean(FrA2ex)),(mean(FrB2ex))];
 
 semmean=std(FrAex)./sqrt(4);
 semmean1=std(FrBex)./sqrt(4);
 semmean2=std(FrA2ex)./sqrt(9);
 semmean3=std(FrB2ex)./sqrt(9);
 err=[semmean,semmean1;semmean2,semmean3];
 
 AandBsumAin=find(AandB==1 & sess==0 & frAbase<0);
 AandBsumA2in=find(AandB==1 & sess==1 & frAbase<0);
 
 FrAin=frAbase(AandBsumAin);
 FrA2in=frAbase(AandBsumA2in);
 FrBin=frBbase(AandBsumAin);
 FrB2in=frBbase(AandBsumA2in);
 
 M2=[(mean(FrAin)),(mean(FrBin));(mean(FrA2in)),(mean(FrB2in))];

 semmean4=std(FrAin)./sqrt(7);
 semmean5=std(FrBin)./sqrt(7);
 semmean6=std(FrA2in)./sqrt(12);
 semmean7=std(FrB2in)./sqrt(12);
 err2=[semmean4,semmean5;semmean6,semmean7];

MA=subplot(2,1,1);
 bar(M);
 hold on
 errorbar=[M,err];
 hold off
 
 MB=subplot(2,1,2);
 bar(M2);
 hold on
 errorbar2=[M2,err2];
 hold off

Answer 1

[Adam Danz]

You aren't plotting the error bars.

Use the errorbar function

errorbar(M, err)

However, you'll need to specify the x values too since your bars aren't on x =1, x=2, etc...

https://www.mathworks.com/help/matlab/ref/errorbar.html

Another tip: When calculating standard error, instead of hard coding the length of FrAex and similar variables (which is a bad idea), just use length(FrAex).

semmean=std(FrAex)./sqrt(length(FrAex));

[Ellen Walker]

Tried this, this is what I get:

MA=subplot(2,1,1);

bar(M);

hold on

errorbar(M,err);

hold off

MB=subplot(2,1,2);

bar(M2);

hold on

errorbar2(M2,err2);

hold off

Index in position 1 is invalid. Array indices must be positive integers or logical values.

[Adam Danz]

What line is producing that error?

[madhan ravi]

errorbar(M2,err2)

[Adam Danz]

Ahhh, I see. "errorbar2" isn't a function. Also, I updated my answer. You'll need to specify the x values of the errorbars since your bars aren't centered on x=1, x=2, etc in the plot you shared.

[Ellen Walker]

Thank you both for your help, but I still don't understand what to do to make the error bars appear on the graph.

I am not sure what you mean by 'x' values

[Adam Danz]

First, take 2-3 minutes to read through the documentation on errorbar(). This should always be step 1 when using a new function. Here's that link again.

https://www.mathworks.com/help/matlab/ref/errorbar.html

The plot you shared doesn't look like it was produced by the code you shared so I'm not sure how the bars on your barchart are centered. If bars 1 to n are not centered on x=1 to x=n, then you'll need to provide the x-values in the errorbar function.

If you still have trouble after reading through the documentation, provide the code here and describe the results (or inlucde another screen shot).

[Ellen Walker]

Thank you, this helped!

[Steven Lord]

This error message:

Index in position 1 is invalid. Array indices must be positive integers or logical values.

suggests to me that you didn't clear the workspace after running your original code (which defined a variable named errorbar) and the updated code (which tries to call the errorbar function.) In that case, MATLAB will treat errorbar(M,err) as an attempt to index into the variable. Using clear to clear the variable errorbar before running the updated code should resolve the problem if I'm correct about the cause.