How do I select every nth number of trials and put them in a separate column?
14 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
I have 180x4 matrix that is sorted by two columns. There are 5 levels or variable A and 6 levels of variable B (30 groups total). Variables C and D are just responses. I would like to sample from each group with replacement. E.g. This would mean that if had a loop with 30 iterations, I would select a sample from each of the 30 groups. If I had 60 iterations, I would select 2 samples from each group.
0 Kommentare
Akzeptierte Antwort
KSSV
am 2 Dez. 2016
For a vector
X = rand(100,1) ;
X10 = X(1:10:end) ; % pick every 10'th value
X7 = X(1:7:end) ; % pick every 7'th value
For a matrix
X = rand(180,4) ;
X10 = X(1:10:end,:) ; % pick every 10'th row
X9 = X(1:9:10,:) ; % pick every 9th row
4 Kommentare
Weitere Antworten (1)
per isakson
am 2 Dez. 2016
Bearbeitet: per isakson
am 2 Dez. 2016
Try this
>> [ B, S ] = cssm1()
B =
[ 6x2 double] [3x2 double] [6x2 double] [3x2 double] [11x2 double] [9x2 double]
[ 8x2 double] [6x2 double] [9x2 double] [6x2 double] [10x2 double] [5x2 double]
[10x2 double] [2x2 double] [3x2 double] [9x2 double] [ 5x2 double] [4x2 double]
[ 8x2 double] [5x2 double] [5x2 double] [3x2 double] [ 8x2 double] [7x2 double]
[ 8x2 double] [4x2 double] [4x2 double] [5x2 double] [ 3x2 double] [5x2 double]
S =
[1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double]
[1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double]
[1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double]
[1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double]
[1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double] [1x2 double]
where
function [ B, S ] = cssm1()
Create the 180x4 matrix, M
len = 180;
M = nan( len, 4 );
M( :, 1 ) = randi( 5, len, 1 );
M( :, 2 ) = randi( 6, len, 1 );
M( :, 3:4 ) = randn( len, 2 );
Binning
[ N, ~, ~, binX, binY ] = histcounts2( M(:,1), M(:,2), 'BinMethod','integers' );
Populate a bin container, B
B = cell( size(N) );
for ii = 1:5
for jj = 1:6
B{ii,jj} = M( binX==ii & binY==jj, 3:4 );
end
end
Draw one random sample from each group
S = cell( size(B) );
for ii = 1:5
for jj = 1:6
ix = randi( size( B{ii,jj}, 1 ), 1 );
S{ii,jj} = B{ii,jj}( ix, : );
end
end
end
Notes:
- "question could have been phrased better"   I guess this is not a solution to your problem. This is rather an answer to the question in the Body than to that in the Title (subject line).
- "Lets say that you have: X = rand(180,4)"   with floats in column 1 and 2 'BinMethod','integers' need to be changed.
- histcounts2 was introduced in R2015b
- with a 180x4 matrix this function is fast enough(?), despite cell arrays and loops
- "selecting that entire row"   replace B{ii,jj} = M( binX==ii & binY==jj, 3:4 );   by   B{ii,jj} = M( binX==ii & binY==jj, : );
- Finally: see Tables, which support features for binning and more.
0 Kommentare
Siehe auch
Kategorien
Mehr zu Matrix Indexing finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!