Is there a multi-dimensional version of arange/linspace in numpy?
This is just what you are looking for:
matr = np.linspace((1,2),(10,20),10)
This means:
For the first column; from 1 of (1,2) to 10 of (10,20), put the increasing 10 numbers.
For the second column; from 2 of (1,2) to 20 of (10,20), put the incresing 10 numbers.
And the result will be:
[[ 1. 2.]
[ 2. 4.]
[ 3. 6.]
[ 4. 8.]
[ 5. 10.]
[ 6. 12.]
[ 7. 14.]
[ 8. 16.]
[ 9. 18.]
[10. 20.]]
You may also keep only one column's values increasing, for example, if you say that:
matr = np.linspace((1,2),(1,20),10)
The first column will be from 1 of (1,2) to 1 of (1,20) for 10 times which means that it will stay as 1 and the result will be:
[[ 1. 2.]
[ 1. 4.]
[ 1. 6.]
[ 1. 8.]
[ 1. 10.]
[ 1. 12.]
[ 1. 14.]
[ 1. 16.]
[ 1. 18.]
[ 1. 20.]]
If you just want to iterate through pairs (and not do calculations on the whole set of points at once), you may be best served by itertools.product
to iterate through all possible pairs:
import itertools
for (xi, yi) in itertools.product(x, y):
print(xi, yi)
This avoids generating large matrices via meshgrid
.
I think you want np.meshgrid
:
Return coordinate matrices from coordinate vectors.
Make N-D coordinate arrays for vectorized evaluations of N-D scalar/vector fields over N-D grids, given one-dimensional coordinate arrays x1, x2,..., xn.
import numpy as np
x = np.arange(-5, 5.1, 0.5)
y = np.arange(-5, 5.1, 0.5)
X,Y = np.meshgrid(x,y)
you can convert that to your desired output with
XY=np.array([X.flatten(),Y.flatten()]).T
print XY
array([[-5. , -5. ],
[-4.5, -5. ],
[-4. , -5. ],
[-3.5, -5. ],
[-3. , -5. ],
[-2.5, -5. ],
....
[ 3. , 5. ],
[ 3.5, 5. ],
[ 4. , 5. ],
[ 4.5, 5. ],
[ 5. , 5. ]])
You can use np.mgrid
for this, it's often more convenient than np.meshgrid
because it creates the arrays in one step:
import numpy as np
X,Y = np.mgrid[-5:5.1:0.5, -5:5.1:0.5]
For linspace-like functionality, replace the step (i.e. 0.5
) with a complex number whose magnitude specifies the number of points you want in the series. Using this syntax, the same arrays as above are specified as:
X, Y = np.mgrid[-5:5:21j, -5:5:21j]
You can then create your pairs as:
xy = np.vstack((X.flatten(), Y.flatten())).T
As @ali_m suggested, this can all be done in one line:
xy = np.mgrid[-5:5.1:0.5, -5:5.1:0.5].reshape(2,-1).T
Best of luck!