Does this variable exist

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Andrea Daou
Andrea Daou am 31 Aug. 2020
Kommentiert: Andrea Daou am 1 Sep. 2020
Hello,
Is it possible to check if a sub variable of a variable existing in the workspace exists?
For exemple 'layers' variables exist in the workspace, how can I put a condition on the existance of layers(k).Weights ?
I know that exist('layers','var') is used to check the existance of variables in workspace.
Thank you! Appreciate any help!

Akzeptierte Antwort

Stephen23
Stephen23 am 31 Aug. 2020
Bearbeitet: Stephen23 am 31 Aug. 2020
  2 Kommentare
Steven Lord
Steven Lord am 31 Aug. 2020
For objects see isprop to determine if the property exists. This is particularly useful for classes with dynamic properties. As an example, define a class:
classdef sometimesX < dynamicprops
methods
function obj = addpropX(obj, xval)
addprop(obj, 'X');
obj.X = xval;
end
end
end
and use that class:
>> y = sometimesX
y =
sometimesX with no properties.
>> isprop(y, 'X')
ans =
logical
0
>> y = addpropX(y, 42)
y =
sometimesX with properties:
X: 42
>> isprop(y, 'X')
ans =
logical
1
Andrea Daou
Andrea Daou am 1 Sep. 2020
Thank you for your help! I used isprop and it worked.

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Peter O
Peter O am 31 Aug. 2020
Bearbeitet: Peter O am 31 Aug. 2020
For structures, use isfield()
clear a
a.M = 'hat';
isfield(a,'M') % True
isfield(a,'N') % False
For array size, use length(a) to find the longest dimension of a, or size(a,d) to find the length of the dth dimension (1=row, 2=col, 3=page, 4... etc). To get the total number of elements, use numel(x). Above you are using a struct array. For your use case:
if numel(layers) < k || ~isfield(layers,'Weights')
% handle undersize struct and/or missing field here
end

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