Conversion to double from struct is not possible

I am trying to concatenate (1080 *1)features for 1000 images.I have tried the following code but it shows error as Conversion to double from struct is not possible at Xall(:, i) = X;

 d = dir('*.mat');
 Xall = nan(1080, 1000);
 for i = 1:length(d)
   X=load(d(i).name);
   Xall(:, i) = X; % assuming that the 1x1080 vectores are stored in X
 end

please give some idea about it.

[kash]

Type X in command window and post the variables.u an see the values in some variable,

Answer 1

[Walter Roberson]

When you use load() of a .mat file and assign the output to a variable, the resulting variable is a structure that has one field for each variable that was stored in the file. So if the variable in the file was "X" then you are going to get a field named "X" inside your structure "X".

Answer 2

[Jan]

A standard method to solve such problems:

Type this in the command window:

dbstop if error

Then start your program again. Matlab stops, when the error occurs and you can inspect the locally used variables in the workspace browser or in the command window:

class(X)
size(x)
X

Then, as Walter has explained already, something like this could be the solution:

Xall(:, i) = X.X;