How to loop over a function again?

I have a pre-written function in matlab which is of the form : function [shortestPaths, totalCosts] = kShortestPath(netCostMatrix, source, destination, k_paths) [K-Shortest Path- Yen's algorithm by Meral Sh.] How to make this function loop for a number of 'sources' and 'destinations' without manually giving in the input each time. I tried something like this:

    function loop(N)
global netCostMatrix
for ii = 1:N
    for iii=1:N
        source = ii;
        destination = iii;
        [sii,tiii] = kShortestPath(netCostMatrix, source, destination,3);
    end
end
    function [shortestPaths, totalCosts] = kShortestPath(netCostMatrix, source, destination, k_paths)
  %...... the code for kshortest path comes here.....
end

This doesn't seem to work. Also, the variables in each iteration should be combined and listed as 2 column matrix - with shortest paths in one and total costs in other. Thank you for your time and help.

[Guillaume]

It's completely unrelated to the question but netCostMatrix should be an input to the loop function. There is absolutely zero reason for it to be global in the above case.

Answer 1

[Ganesh Hegade]

HI,

You are not returning any output from the function loop.

function  [ShortestPath, TotalCost] = loop(N)
 global netCostMatrix
   for ii = 1:N
    for iii=1:N
        source = ii;
        destination = iii;
        [shortestPaths, totalCosts] = kShortestPath(netCostMatrix, source, destination,3);
        ShortestPath(ii, iii)= shortestPaths; 
        TotalCost(ii, iii) = totalCosts;
    end
   end
 end % loop

If the netCostMatrix is already present in the workspace then you can pass this also as input for function loop.

function [shortestPaths, totalCosts] = loop(N, netCostMatrix )
end %loop

Thanks.

[Hari]

Thanks. It works. But the output variable stores only the result from the last value in the loop. Is there a way to store all the output values.

[Ganesh Hegade]

Hi,

Try this

function  [ShortestPath, TotalCost] = loop(N)
 global netCostMatrix
   for ii = 1:N
    for iii=1:N
        source = ii;
        destination = iii;
        [shortestPaths, totalCosts] = kShortestPath(netCostMatrix, source, destination,3);
        ShortestPath(ii, iii)= shortestPaths; 
        TotalCost(ii, iii) = totalCosts;
    end
   end
 end % loop

[Hari]

It doesn't seem to work. Shows an error message:

    >> [ShortestPath, TotalCost] = loop1(5)
Subscripted assignment dimension mismatch.
Error in loop1 (line 8)
        ShortestPath(x, y)= shortestPaths;

[Ganesh Hegade]

I Think the size of shortestpaths and totalCosts are not equal. Store output of loop in an cell array and check, else put a break point atbefore end of function and check whether dimensions of ShortestPath and TotalCost are equal. Size of these 2 matrix should be equal.

[Hari]

Sorry I'm new to MATLAB. When I checked using 'whos' function this is what I got: Shortest path is having class CELL with dimension 3 x 1 and total costs is class DOUBLE with dimension 3 x 1.

Answer 2

[Guillaume]

Probably a simpler way of writing these loops would be with:

function loop(N, netCostMatrix)  %where are the outputs?
  %netCostMatrix shouldn't be global, passing it as input here
  [source, destination] = ndgrid(1:N);
  [shortestPaths, totalCosts] = arrayfun(@(src, dest) kShortestPath(netCostMatrix, src, dest, 3), 'UniformOutput', false);
end

If the outputs or kShortestPath are both scalar, then you can omit the 'UniformOutput', false

Answer 3

[indu]

i am facing the same problem.Hope you have found out the solution for the above problem.If so can you please post the answer .