CODEWITHSUNDEEP
pythonnumpy
user401247
user401247

Reputation:

How to add a random number to a subsection of a numpy array?

I'm new to Python.

I have a numpy array of 3 columns and 50 rows. I want to add a value drawn from a normally distributed distribution to every number in the array except the first row. I am curious to know if there is a cleaner but also readable way to do this compared what I am currently doing? At the moment I'm using perhaps the not so elegant way:

 nRows = np.shape (data)[0]  
 nCols = np.shape (data)[1]  
 x = data[0,:].copy()  # Copy the first row
 # Add a random number to all rows but 0
 for i in range (nCols):
     data[:,i] += np.random.normal (0, 0.8, nRows)
 data[0,:] = x # Copy the first row back

Upvotes: 0

Views: 68

Answers (1)

akuiper
akuiper

Reputation: 214987

You can assign values to indexed array. For your case, generate the 2d random array first and then directly add it to sliced data:

data[1:] += np.random.normal(0, 0.8, (nRows - 1, nCols))

Upvotes: 1

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