Standard deviation in each quartile of a dataset

Say I have a dataset (an array of 1 row by say, x, columns) that I want to divide into 4 quartiles.

How can I divide it into quartiles and compute the standard deviation of the data in each quartile, then plot the resulting standard deviations as a bar plot with the quartiles on the x-axis and standard deviation values on the y-axis?

Thank you in advance, all help is appreciated!

Answer 1

[Image Analyst]

Not sure what you mean by quartile but maybe it's 1/4 of the sorted data. If so, try this:

vec = sort(yourOriginalVector);
numElementsPerQuartile = numel(vec)/4;
stDev(1) = std(vec(1 : numElementsPerQuartile));
stDev(2) = std(vec(numElementsPerQuartile + 1 : 2 * numElementsPerQuartile));
stDev(3) = std(vec(2*numElementsPerQuartile + 1 : 3 * numElementsPerQuartile));
stDev(4) = std(vec(3*numElementsPerQuartile + 1 : end));
bar(stDev);
grid on
ylabel('Standard Deviation')

[mickeymouse]

Thank you, this is exactly what I wanted to do!