CODEWITHSUNDEEP
pythonnumpymatrixscipy
obtmind
obtmind

Reputation: 287

Append sum of rows and columns to matrix

I have (n,n) numpy array. I want to append a column vector where each element in it is the sum of the corresponding rows. I also append a row vector to the end of the matrix which is a sum of the corresponding columns. However, appending these 1D arrays is not compatible from a dimensional stand point. I want to append these, but have a matrix where the point (-1,-1) is the sum of either the last row or column (as they are equal).

Example;

x = np.random.randint(5, size=(4, 4))
columns = np.sum(x,axis=1)
rows = np.sum(np.transpose(x),axis=1)

Upvotes: 2

Views: 2859

Answers (1)

Miriam Farber
Miriam Farber

Reputation: 19634

You can do it like that: First let's generate some matrix a

n=5
k=4
a=np.zeros([n,k])
for i in range(n):
    for j in range(k):
        a[i][j]=i+2*j

Then run the following commands. This adds the row:

a=np.append(a,[np.sum(a,axis=0)],axis=0)

This calculates the column

col=np.array([np.sum(a,axis=1)])

Finally we add the column

a=np.concatenate((a,col.T),axis=1)
print(a)

Note that this takes care of the (-1,-1) entry as well.

Upvotes: 2

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