"I have a matrix [a b c d f], size of each element is 200x16"
Does this mean you have a cell array containing six 200x16 matrices?
"I need to get a single boxplot where a, b, c, d, f will be plotted against five different label"
I don't understand this part. Do you want a single box plot or you want a single plot with several boxes on it? What labels are you refering to?
