How to take the average of the columns of a matrix and insert into a column matrix

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Feliciano Döring
评论： Star Strider 2018-7-3
I have a piece of code that reads a .txt file with several matrices and sorts them into cell arrays. Each of the matrices has always three columns with varying rows. My question would be how i can take the average of the first two columns column from these matrices separately and put it in a column matrix that would always start the row with 0 and then the average of the first column, followed by the average of the second column and then a value that i would insert with a prompt or something. One more thing is that the last value of this new column matrix is also something that i would insert. Here's the code for the code and the .txt file is indexed.
filepath = '/Users/...';
fileID = fopen(filepath);
nGroups = 0;
stationGroups = cell(0,1);
while true
nStations = fgets(fileID);
if ~ischar(nStations)
break;
end
nGroups = nGroups + 1;
nStations = str2num(nStations);
stationMatrix = zeros(nStations,3);
for currentStation = 1:nStations
fprintf('Loading station %d of station group %d: ', ...
currentStation, nGroups);
testStation = fgets(fileID);
if ~ischar(testStation)
error('Error - file ended too early!');
end
testStation = str2num(testStation);
if numel(testStation)~=3
error('Error - Station %d didn''t have three values!', ...
currentStation);
end
fprintf('%.2f ',testStation);
fprintf('\n');
stationMatrix(currentStation,:) = testStation;
end
stationGroups{end+1} = stationMatrix;
nGroups = length(stationGroups);
end
fclose(fileID);
The format of the column matrix would then be(for if i choose only the first two matrices of the file):
0
average of the first column
average of the second column
value that i insert
0
average of the first column
average of the second column
value that i insert
another value that i insert
practically it would look like this:
0
0.397309273000000
9.579781409000001
-0.008595000000000
0
0.397309273000000
9.579781409000001
-0.008595000000000
0.005900000000000

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采纳的回答

Star Strider
Star Strider 2018-7-3
A slight variation on my previous code works here:
fidi = fopen('file.txt','rt');
c = textscan(fidi, '%f%f%f', 'Delimiter',' ', 'CollectOutput',1);
fclose(fidi);
d = [c{:}]; % Can Use ‘cell2mat’ Here As Well
bk = any(isnan(d), 2); % Rows With ‘any’ NaN Columns
nr = d(bk,1); % Number Of Rows In Next Segment
de = d(~bk,:); % Eliminate Rows With NaN Columns
mtx = mat2cell(de, nr, 3); % Use Those Data To Create The ‘mtx’ Matrix
OutC = cellfun(@(x)[0 mean(x(:,[1 2])) NaN]', mtx, 'Uni',0); % Cell Array Of Mean Values
OutM = cell2mat(OutC); % Double Array Of Mean Values
OutM =
0
3.97e+05
9.5811e+06
NaN
0
3.9831e+05
9.5775e+06
NaN
...
Put your other inserted values in the NaN positions. The easiest way would be to create them in a (nnz(bk)x1) vector, and then assign them to the NaN values in the ‘OutM’ vector:
Added = rand(nnz(bk),1); % Use Random Values To Test
OutM(isnan(OutM)) = Added;
  2 个评论
Feliciano Döring
Feliciano Döring 2018-7-3
编辑：Feliciano Döring 2018-7-3
Thanks again! Just one more thing, how would i add the last value? just assigning OutM to a variable like m=[OutM;value];?
Star Strider
Star Strider 2018-7-3
As always, my pleasure!
The easiest way to add the last value would be to create a vector for all of them that is nnz(isnan(OutM)) long, (that is, with dimension (nnz(isnan(OutM)) x 1)). Then write it to ‘OutM’ as I illustrated with the ‘Added’ vector earlier.
Otherwise, the indices of the NaN values are:
NaNidx = find(isnan(OutM));
and you could use that to write to any of them individually, so if you wanted to write ‘m’ to NaN #3:
OutM(NaNidx(3)) = m;
I tested that to be certain. It works.

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