problem with undefined variable in for loop.

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lina
lina 2014-4-2
评论： lina 2014-4-2
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.

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回答（1 个）

Walter Roberson
Walter Roberson 2014-4-2
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.
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Walter Roberson
Walter Roberson 2014-4-2
编辑：Walter Roberson 2014-4-2
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
lina 2014-4-2
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?

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