MATLAB: Finding length of a struct, excluding NaN values

lengthMATLABnan

I have a struct with the following layout:

T X Y

[0,1] [0, 1] [0,5]

[0] [2] [2]

NaN NaN NaN

I want to find the length of the struct excluding the trailing NaN values at the bottom. So in this case the length would be 2 instead of 6.

I have attached a file with some of the values that I am using and the struct shape. Thanks

Best Answer

You can do this very easily with the accepted answer to your very similar question from two months ago:

https://www.mathworks.com/matlabcentral/answers/459653-removing-nans-from-a-struct

Just use the logical variable X:

>> F = @(s)all(structfun(@(a)isscalar(a)&&isnan(a),s)); % or ANY
>> X = arrayfun(F,AllData.Passive)
X =
  0  0  0  0  1  1  1  1  1  1  1  0  0  0  0
>> nnz(~X)
ans = 8

Related Solutions

MATLAB: Removing NaNs from a struct

This works for any sized fields (including empty), and gives you the choice of matching ALL or ANY of the fields containing NaN.

>> F = @(s)all(structfun(@(a)isscalar(a)&&isnan(a),s)); % or ANY
>> X = arrayfun(F,AllData.Passive);
>> AllData.Passive(X) = [];

checking:

>> AllData.Passive.T
ans =
     0     1     2     3     4     6     7     8     9    10
ans =
     0     3     4     7     9    10
ans =
     0     2     6
ans =
     0     1     6     7     8
ans =
    10
ans =
    10
ans =
    10
ans =
    10

MATLAB: Removing data from a structure that is less than a certain threshold

The iterative growing and shrinking of arrays is extremely expensive. Better:

nTraj  = numel(AllTraj.Passive);
remove = false(1, nTraj);
for c = 1:nTraj
    tmp       = AllTraj.Passive(c).T;
    % [EDITED: remove -> remove(c)]
    remove(c) = (numel(tmp) <= 10) && (max(tmp) < (i-2));
end
AllTraj.Passive(remove) = [];

Remember: To create a growing array, e.g.:

x = [];
for k = 1:1e6
    x(k) = rand;
end

Matlab has to reserve sum(1:1e6)*8 bytes in the RAM and copy almost the same amount of memory. This is 4 TeraByte, although the final array has 8 MB only. Of course this is slow.

The solution is a pre-allocation:

x = zeros(1, 1e6);

Or in your case to collect the indices to remove at first and remove them in one step after the loop.

Best Answer

Related Solutions

MATLAB: Removing NaNs from a struct

MATLAB: Removing data from a structure that is less than a certain threshold

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