MATLAB: Determine total length/size of a structure array with fields as structure arrays
This will work if every structure array data
has the same fields and are row vectors (i.e. 1-by-N):
allData = [s.data]; %# Concatenate all data arrays into one
timestamp = [allData.timestamp]; %# Collect all the time stamps
If the data
structure arrays are column vectors (i.e. N-by-1), you need to use vertcat
instead:
allData = vertcat(s.data); %# Concatenate all data arrays into one
timestamp = [allData.timestamp]; %# Collect all the time stamps
The above solutions work due to the fact that accessing a single field of a structure array returns a comma-separated list.
Doresoom
Mechanical Engineer from St Louis, MO. Former NASA flight controller for the International Space Station.
Updated on March 30, 2020Comments
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Doresoom about 4 years
I have a structure array containing fields as structure arrays of varying length. For example:
's' is a structure 'data' is a field in 's', and also a structure array itself and
length(s(n).data) ~= length(s(m).data)
I want to preallocate an array that takes a time stamp from every field s.data.timestamp. Is there a way to do this without using a for loop twice? This is what I have so far:
% find the total length count=0; for x=1:length(s) count=count+length(s(x).data); end % preallocate timestamp array timestamp=zeros(1,count); % populate timestamp array index=1; for x=1:length(s) for y=1:length(s(x).data) timestamp(index)=s(x).data(y).timestamp; index=index+1; end end
I thought about just overestimating the length that I would need based on the length of 's' and an average length of 'data', but the actual length of each 'data' field/substructure varies widely. Would I be better off just overestimating the heck out of it and trimming the resulting array afterward? Zero timestamps are impossible with the data set I'm working with, so that shouldn't be a problem.
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Doresoom over 14 yearsWow! Only two lines - I believe the term "freakin' genius" may apply here.
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gnovice over 14 years@doresoom: Comma-separated lists are your friends. ;)