count the number of unique elements

Question

Elysi Cochin 2022-6-3

回答： Walter Roberson 2022-6-3

I have a matrix with 2 rows 23 columns

M = [3,2,3,3,2,3,3,2,4,3,3,3,1,1,1,3,4,4,3,5,5,3,3;1,1,1,1,1,1,1,1,1,2,2,2,3,3,4,4,4,4,5,5,6,6,6];

Now i'll take all columns where column = 1 in row2

3	2	3	3	2	3	3	2	4
1	1	1	1	1	1	1	1	1

and i need to count the number of unique elements in so much columns, and also convert into its percentage

= 0
= 3
= 5
= 1
= 0

percentage computation

0/9 *100
3/9 *100
5/9 *100
1/9 *100
0/9 *100
% where 9 is the number of columns with column value 1 in row2

then take all columns where column = 2 in row2

3	3	3
2	2	2

then take all columns where column = 3 in row2 and upto 6

Row1 has unique values 1 to 5, and

Row2 has unique values 1 to 6

Answer 1

Walter Roberson 2022-6-3

counts = accumarray(M([2 1],:) .', ones(size(M, 2),1))
perc = counts ./ sum(counts, 2) * 100

Rows of perc will correspond to values in row 2 of M. Columns will correspond to values in row 1 of M.

The code should be made more robust for the case where the values are not consecutive positive integers.