scipy -- how to insert an array of zeros into another array with different dimensions

Question

If i have an array:

myzeros=scipy.zeros((c*pos,c*pos))  , c=0.1 , pos=100

and an array:

grid=scipy.ones((pos,pos))

How can i insert the zeros into the grid in random positions? The problem is with the dimensions.

I know that in 1d you can do:

myzeros=sc.zeros(c*pos) # array full of (zeros)
grid=sc.ones(pos)         # grid full of available positions(ones)
dist=sc.random.permutation(pos)[:c*pos] # distribute c*pos zeros in random
                                        # positions
grid[dist]=myzeros

I tried something similar but it doesn't work. I tried also: myzeros=sc.zeros(c*pos), but it still does not work.

xubuntix · Accepted Answer · 2011-11-09 12:43:52Z

3

There are several ways, but the easiest seems to be to first convert the 2D grid into a 1D grid and proceed as in the 1D case, then convert back to 2D:

c = 0.1
pos = 100
myzeros=scipy.zeros((c*pos,c*pos))
myzeros1D = myzeros.ravel()
grid=scipy.ones((pos,pos))
grid1D = grid.ravel()
dist=sc.random.permutation(pos*pos)[:c*pos*c*pos]
grid1D[dist]=myzeros1D
myzeros = myzeros1D.reshape((c*pos,c*pos))
grid = grid1D.reshape((pos, pos))

EDIT: to answer your comment: if you only want a part of the myzeros to go into the grid array, you have to make the dist array smaller. Example:

dist = scipy.random.permutation(pos*pos)[:c*pos]
grid1D[dist] = myzeros1D[:c*pos]

And I hope you are aware, that this last line can be written as

grid1D[dist] = 0

if you really only want to set those elements to a single instead of using the elements from another array.

edited Nov 9, 2011 at 12:43

answered Nov 8, 2011 at 17:29

xubuntix

2,33318 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

George Over a year ago

:Hello, when i run the last command it gives me "grid = grid1D.reshape((cpos, cpos))" ..Any ideas?Thanks!

xubuntix Over a year ago

Hi, I'm not sure what you mean by that, but I have had an error in the last line. Maybe you just forgot to press enter ofter the last line?

George Over a year ago

:I had a typo error.It works.But the problem is that i want to insert cpos zeros into the grid=scipy.ones((pos,pos)).With the above ,it inserts the number of shape of the myzeros array (cpos cpos) into the grid.I can't figure a way to do that!

George Over a year ago

:Exactly what i want!Thanks a lot.Also,it doesn't need to be created the myzeros=scipy.zeros((cpos,cpos)).It can be done with 1D myzeros.(this goes about my second question).

Collectives™ on Stack Overflow

scipy -- how to insert an array of zeros into another array with different dimensions

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related