addBar

add error bars to a simple graph

Use this simple code to easily add standard error bars to an existing 2D graph.
You can determine the visual length of the bars, whether they are symmetric or only one sided, and whether they are vertical (the common case) or horizontal. You will need to pre-compute the averages and standard errors of your existing data, and plot the averages, before using this function to add the bars.
EXAMPLE:
Assume you measured the effects of different treatments on 3 groups, with 20 subjects
each. The data is stored in grp1, grp2 and grp3 (each is a 20x1 vector). Then, compute:
dataX = [1 2 3];
average of each group: dataY = [mean(grp1) mean(grp2) mean(grp3)];
standard error of each group: dataS = [std(grp1) std(grp2) std(grp3)]/sqrt(20);
bar plot of the averages: bar(dataX, dataY).
Then use this code to add error bars with: addBar(dataX,dataY,dataS,0.05,0)