I have a very quick question about the notation on accessing an array in python.
Is this line:
trainPredictPlot[look_back:len(trainPredict) + look_back, :] = trainPredict
I've seen arrays are being accessed like this x[a:b] but never like this x[a:b,:]
Can someone explain me with detail what this line of code is doing? What does it mean to put colon before the closing bracket? What about the comma?
asked Mar 30, 2017 at 3:17
Pablo Estrada
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1 Answer 1
When you use x[a:b], it means that you are taking the elements from position "a" (x[a]) to position "b" (x[b]) of a one dimensional array. For the second case x[a:b,:], it is a two dimensional "a" to position "b" of the first dimension of the array, and all the elements of the second dimension of the array, in other words, from x[a][first element] to x[b][last element].
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1 Comment
Pablo Estrada
Thanks for your answer. Expanding on that notation then is it possible to add as many comas as dimensions my array has?
lang-py
m[a:b, :]. Note the comma. See docs.scipy.org/doc/numpy/reference/arrays.indexing.html