There are a few problems that I see:
1. In MATLAB, return doesn't take arguments, so you don't say
return (mean, median; stddev; min_val; max_val);
You just say
return
and the vaues that are returned from the function (i.e., the output arguments of the function) are defined in the function definition, as you are doing
function [mean, median, stddev, min_val, max_val] = central_dispersion_measurements(data)
% ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ outputs
However, in this case, since the return statement is at the end of the function, you don't need it at all. You can remove it entirely.
2. Don't use mean and median as variable names, since they are names of built-in functions that you need to use. Replace those variable names with other names that don't conflict with built-in MATLAB functions, such as mean_data and median_data, for example.
3. The show function is for displaying information about an optimization object, not for making graphics show up or whatever you intended. You don't need to do anything special to make graphics show up, just create them (e.g., using histogram or bar, like you do here). Remove the show lines.
4. For robustness (i.e., correctly handling the case that data has only one row), you should specify that you want to take the mean, median, etc., over the rows of data by specifying dimension 1 in those functions. That is:
mean_data = mean(data,1);
median_data = median(data,1);
stddev = std(data,0,1);
min_val = min(data,[],1);
max_val = max(data,[],1);
There may be other problems. If you run into other problems, upload your data file here (using the paperclip button).
