Need to create lists out each row of a matrix

Community Support
1

Hello,

How may I create a list of lists, each inner list being a row of a matrix?

eg: 

matrix : 

1 2 

2 3

4 5

4 6

result-> 

((1;2);(2;3);(4;5);(4;6))

Thanks, 

Kumar

2

Hi Krishna,

Not exactly sure what you mean here, the example you have given is a list of lists (i.e. a matrix):

q)((1;2);(2;3);(4;5);(4;6))

1 2

2 3

4 5

4 6

If you wish to create a list of lists/matrix from a single list consider using # with the dimensions of the matrix:

q)(4 2)#til 8

0 1

2 3

4 5

6 7

For an unknown length you may use:

q)(0N 2)#til 8

0 1

2 3

4 5

6 7

Which gives an equivalent result to using cut:

q)2 cut til 8

0 1

2 3

4 5

6 7

Regards,

Thomas Smyth

AquaQ Analytics

3

Thanks, Thomas. 
Let me clarify:
I want to treat a row of a matrix as an index into another matrix.

q) a:((1;2);(2;3);(4;5);(4;6))

q) b:6 6 # til 36(for example)

I want to use each element of ‘a’ as a (row;column) pair. 

In my case, when I do b[a[0]], I get 

6  7  8  9  10 11

12 13 14 15 16 17, 

when , actually I want b[1;2] -> 8. 

Regards, 

Krishna

4

Little roundabout code:
a:((1;2);(2;3);(3;5);(4;6)) -> matrix containing indices (row;col) pairs.

rows:500

cols: 10

z:(rows*cols) # 0;

z[(cols*a[;0])+a[;1]]:1; -> 

z:(rows,cols]#z;

My two pence. 

Kumar

5

Hi,

You could use either of the following:

q)b ./: a

8 15 29 0N

q).[b;] each a

8 15 29 0N

Regards,

Thomas Smyth

AquaQ Analytics

6

Much appreciated, Thomas. 
Regards, 

Kumar