Output argument "u" (and maybe others) not assigned during call

Error in spm_u (line 23)
if     STAT == 'Z'

Output argument "u" (and maybe others) not assigned during call to "C:\spm5\spm5\spm_u.m>spm_u".

Error in spm_getSPM (line 654)
            u = spm_u(u^(1/n),df,STAT);

Error in spm_results_ui (line 275)
  [SPM,xSPM] = spm_getSPM;

Error while evaluating uicontrol Callback

• * * * >>

The above error is displayed when I try to load up the SPM.mat file in the 'Results' GUI in SPM5. Below is the spm_u function** * * * *

function [u] = spm_u(a,df,STAT)
% uncorrected critical height threshold at a specified significance level
% FORMAT [u] = spm_u(a,df,STAT)
% a     - critical probability - {alpha}
% df    - [df{interest} df{error}]
% STAT  - Statistical field
%               'Z' - Gaussian field
%               'T' - T - field
%               'X' - Chi squared field
%               'F' - F - field
%
% u     - critical height {uncorrected}
%___________________________________________________________________________
% spm_u returns the uncorrected critical threshold at a specified significance
%
%___________________________________________________________________________
% Copyright (C) 2005 Wellcome Department of Imaging Neuroscience

% Karl Friston
% $Id: spm_u.m 707 2006-12-06 16:42:20Z volkmar $

if     STAT == 'Z'

  u   = spm_invNcdf(1 - a      );

elseif STAT == 'T'

  u   = spm_invTcdf(1 - a,df(2));

elseif STAT == 'X'

  u   = spm_invXcdf(1 - a,df(2));

elseif STAT == 'F'

  u   = spm_invFcdf(1 - a,df   );

elseif STAT == 'P'

  u   = a;

end

Answer 1

[Walter Roberson]

You left out the error message before

Error in spm_u (line 23)

You are probably calling spm_u without passing in three parameters. We would need to see your callback to say more.

[m_asghar]

I'm possibly way out of my depth here - I'm just using GUIs. How do I show you my callback?

[Walter Roberson]

Attach the .m file

Answer 2

[Guillaume]

if stat is neither 'Z' , 'T', 'X', 'F' or 'P' then indeed the output u won't be assigned any value.

You can fix the problem with the obscure error message by adding another else condition to your code:

%...your code, ending with:
elseif STAT == 'P'
   u = a;
else %error?
   error('input argument STAT contains invalid value: %s', STAT);
end

That won't solve the underlying problem that you're passing an invalid STAT value to the function.

By the way, your if...elseif...elseif...else would probably be better written as a switch...case...otherwise statement.