problem with undefined variable in for loop.

hi,

I have problem here for undefined variable

   for i=1:41
ncload(['wod_00',num2str(cast(i)),'O.nc']);
% pause
[n,m]=size(Temperature);

 if lat<20;

    (~exist('Pressure'))
    t(1:n,i)=Temperature(:);
    sal(1:n,i)=Salinity(:);
    Z(1:n,i)=z(:);

 else lat>20
    t(1:n,i)=Temperature(:);
    Z(1:n,i)=z(:);

        if exist('Salinity', 'var')
           sal(1:n,i)=Salinity(:);

        else exist('Pressure','var');
           p(1:n,i)=Pressure(:);

        end
    end               
 end

thank you.

Answer 1

[Walter Roberson]

Which variable, and at which point?

Note that

(~exist('Pressure'))

tests whether Pressure exists as any of a number of kinds of object, then takes the logical negation of the result, and displays it to the screen, without using it in computation.

Some of your files might have variables defined that others do not. You should be clear'ing variables that are potentially loaded from the file, as otherwise the data from the previous file might be still be in memory.

[lina]

ok, i got the point

the variable is sal and p, in the second if statement، the Matrix appears empty are no values, such as those in t and z those are define in first if statement.

Thank very much for your help Mr. Walter

[Walter Roberson]

Note that

else lat>20

is the same as

else
  disp(lat>20)

and

else exist('Pressure','var');

is the same as

else
  exist('Pressure','var');   %calculate result and throw it away

[lina]

so i don't need to use it here even if i write

 else exist('Pressure','var');

because it doesn't show me any values is it right?