Adding random data to left and right of each element in a matrix
7 views (last 30 days)
Show older comments
This is a change from my previous question with random elements instead of fixed elements
Take for example,
i have two 3x4 matrices, M=
1 2 3 4
5 6 7 8
9 10 11 12
and E which shows the number of elements to be added to matrix M, random from 1-4
4 2 1 2
2 3 4 1
1 3 2 3
The elements to be added are random numbers from 0.1 to 0.9, the result to be obtained is shown below
1.3 1.9 1.4 1.1 1 1.5 1.3 1.9 1.7 2.2 2.4 2 2.9 2.5 3.1 3 3.7 4.8 4.2 4 4.4 4.1
5.3 5.8 5 5.5 5.1 6.6 6.1 6.3 6 6.2 6.2 6.7 7.2 7.3 7.2 7.9 7 7.1 7.5 7.4 8.8 8 8.2
9.2 9 9.5 10.9 10.7 10.6 10 10.4 10.3 10.4 11.3 11.4 11 11.1 11.9 12.3 12.9 12.5 12 12.3 12.4 12.8
Next is how do i store this data since it no longer stays as a matrix and is it possible use indexing to find a certain value eg. find(M==2)
1 Comment
Accepted Answer
Stephen23
on 16 Nov 2017
Edited: Stephen23
on 16 Nov 2017
M = [
1 2 3 4
5 6 7 8
9 10 11 12];
E = [
4 2 1 2
2 3 4 1
1 3 2 3];
%
foo = @(m,e) m+randi(9,1,e)/10;
fun = @(m,e) [foo(m,e),m,foo(m,e)];
C = arrayfun(fun,M,E,'Uni',0);
Giving the output in a cell array C, where each cell contains a vector based on one element of M, e.g. the first column of C:
>> C{:,1}
ans =
1.4000 1.3000 1.9000 1.3000 1.0000 1.9000 1.1000 1.3000 1.9000
ans =
5.6000 5.6000 5.0000 5.9000 5.5000
ans =
9.1000 9.0000 9.3000
>>
" how do i store this data since it no longer stays as a matrix..."
I showed you how to put this into a cell array which is the same size as your original matrices. Alternatively you could extract all of the numeric data and concatenate it into one long numeric vector.
"...and is it possible use indexing to find a certain value eg. find(M==2)"
That depends on how your decide to store it: storing in a cell array requires a different way of searching than if you use one numeric vector.
6 Comments
Stephen23
on 16 Nov 2017
Use a cell array, add it as an input to cellfun. something like this::
H = {[0.2 0.8 0.3 0.5],[10,20],...}
M = [...];
fun = @(m,h) [fliplr(h)+m,m,m+h];
cellfun(fun,num2cell(M),H,'Uni',0)
More Answers (1)
Image Analyst
on 16 Nov 2017
Since the padding on either side of each element of M is determined by the value of the corresponding element of E, and the sum of the rows in E do not sum to a constant, the rows in the final result will probably not all be the same length. Thus you will need to use a cell array.
It will be very easy for you to do this yourself once you're read the FAQ on cell arrays: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F
2 Comments
See Also
Categories
Find more on Creating and Concatenating Matrices in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!