Unable to change InitialPopulationMatrix in GA problem options

I have a problem called fopt; in fopt.options, fopt.options.InitialPopulationMatrix = [];

fopt.options.InitialPopulationMatrix = 'doubleVector'; and finally, fopt.options.PopulationSize = 340 and

fopt.nvars = 11. So, I have a script where I define a variable w of size 340x11 and then set:

fopt.options.InitialPopulationMatrix = w

Matlab replies with

Invalid value for OPTIONS parameter InitialPopulationMatrix: must be a two-dimensional matrix.

I've tried everything I can to find the proble, but to no avail. Even setting the line just before

fopt.options.InitialPopulationMatrix = w

to

size(w)

returns

ans =

340 11

and ismatrix(w) returns 1..... I've never had any issues setting this property before, so any help greatly appreciated.

[Geoff Hayes]

Tom - how is w initialized? Could it be a cell array which would return the same above answers (for size and ismatrix)?

[Tom Brenner]

Thank you for the reply. Aha! I found the trouble thanks to you! It was not a cell array, but rather was defined from reading numeric values from variables of class SINGLE. Simply changing w into class DOUBLE (w = double(.....).....) solved the issue!

Thank you sir!

Edit: seeing as you posted a comment rather than an answer, I cannot accept it as one.... But obviously you solved my issue.