MATLAB: Would like to add standard error bars to bar graph

error barsMATLAB

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

Best Answer

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));
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