Python for Machine Learning

Image manipulation

• dot producting an array (that represents a colour image) with [0.299, 0.587, 0.144] will convert that image to greyscale.

General Numpy

• The colon is used for specifying a range of values that can then be used to return parts of a matrix. e.g. If a is a 3x3 matrix then a[:1] returns the first row.

• The ellipsis in Python is a placeholder for the rest of the array dimensions not specified. e.g. for a 3d array then a[...,0] is the same as a[:,:0].

• The .shape method returns the dimensions of an array

Convolution

For convolution, TensorFlow accepts images of dimensions: [number of images, width, height, channels].

Plotting

When you have a tensorflow distribution, to plot with a ramge use:

plt.hist(a, 100, (-4.2, 4.2));