Question

I have a set of data and ask Matlab to sort in ascending order like this

filename=input('Type filename.txt: ','s');
fid=fopen(filename);
mydata=textscan(fid,'%f %c','headerlines', 1, 'delimiter','\t');
fclose(fid);

% sort data
[mydata{1},idx] = sort(mydata{1})
mydata{2} =  mydata{2}(idx)

Data came out like this:

0.41    U
0.41    U
0.41    U
0.41    D
0.41    U
0.41    D
0.41    U
0.41    U
0.41    D
0.41    U
0.42    U
0.42    D
0.42    U
0.42    U
0.42    U
0.42    D
0.43    U

U = undetect and D = Detects. If you notice carefully, if the first column has the same number, say 0.41, Matlab would sort the first column and disregard the order of the second column. What I would like Matlab to do is if it sees the same number in the first column, then place the number based on the second column, U first before D.
The final sorted data would like this:

0.41    U
0.41    U
0.41    U
0.41    U
0.41    U
0.41    U
0.41    U
0.41    D
0.41    D
0.41    D
0.42    U
0.42    U
0.42    U
0.42    U
0.42    D
0.42    D
0.43    U

If somehow it would make it easier, I can make 1=Detect and 0=Nondetect
Thank you for your help and time.

Edit: I should also add that sortrow does not work because I would like to preserve the data structure so that the following code would follow

o=mydata{1} %index the first column of the array mydata


c = zeros(size(mydata,1),1); % preallocate empty matrix 
c = mydata{2} == 'U';
for i = 1:size(mydata,1)
 curValue = mydata{i,2};
 data{i,3} =  ~isempty(curValue) && ischar(curValue) && strcmp(curValue ,'U');

end

Answer 1

You can use sortrows, but you have to convert mydata into a n-by-2 cell array first:

mydata = [num2cell(mydata{1}),num2cell(mydata{2})];

cs = sortrows(mydata,[1,-2]) %# sort the first col ascending, then second descending
cs = 
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'U'
    [0.41]    'D'
    [0.41]    'D'
    [0.41]    'D'
    [0.42]    'U'
    [0.42]    'U'
    [0.42]    'U'
    [0.42]    'U'
    [0.42]    'D'
    [0.42]    'D'
    [0.43]    'U'

You can backtransform it by calling

mydataSorted = {cat(1,cs{:,1}),cat(1,cs{:,2})};

Obviously, if you transform your data so that mydata{2} is numeric, you can simply forego the cell array and call sortrows straight away.