Extracting a double array from within a struct
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DD_2023
el 17 de Mzo. de 2024
Comentada: DD_2023
el 18 de Mzo. de 2024
I have a structure of 1x297 with 13 fields. One of those fields is called contains a double array within each cell of the structure (297 times) and that varies in row length (between 300 and 1000), but has 18 columns. This is where it gets complicated...
I want to extract the entire row from each double array, within the struct, where the value in the second column is >= 4 and <= 5.
So in the end I will have an 18x297 array.
Apologies if this isn't very clear. Thank you!
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Stephen23
el 18 de Mzo. de 2024
Editada: Stephen23
el 18 de Mzo. de 2024
"So in the end I will have an 18x297 array."
Because there are a different number of columns in each matrix you will need to EITHER store the extracted rows separately (e.g. in a struct/cell array) OR pad/subsample (e.g. indexing) the rows to make them the same lengths before concatenating into one matrix.
Here is one approach to store the complete rows separately in a cell array:
F = @(m) m(m(:,2)>=4 & m(:,2)<=5,:);
C = arrayfun(@(s) F(s.Data), Struct, 'uni',0);
Or if you want to shorten the rows and concatenate them together:
F = @(m) m(m(:,2)>=4 & m(:,2)<=5,1:18);
C = arrayfun(@(s) F(s.Data), Struct, 'uni',0);
M = vertcat(C{:}).';
Avoid using names like STRUCT which differ only in case to the names of inbuilt functions.
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Image Analyst
el 18 de Mzo. de 2024
Structures have "fields" not "cells".
"One of those fields is called contains..." <== is called WHAT??? You left out the name of the field.
If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:
Assuming your structure is called s, and your unnamed field is called data, you can do
data = s.data;
% Get a logical vector of rows that meet the extraction criteria.
rowsToExtract = data(:, 2) >= 4 & data(:, 2) <= 5;
result = data(rowsToExtract, :); % An Nx18 matrix where N can be as much as 297.
% In the end I want an 18x297 array (18 rows, not columns)
% so we must transpose to get 18 rows, not a variable number of rows.
result = result.'; % Transpose
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