Boolean Indexing Question

[dominic]

Screen Link: https://app.dataquest.io/m/290/boolean-indexing-with-numpy/6/assigning-values-in-ndarrays

taxi_modified = taxi.copy()
taxi_modified[28214, 5] = 1
taxi_modified[:, 0] = 16
taxi_modified[1800:1802, 7] = taxi_modified[:,7].mean()

I was just wondering on the last line where we select rows 1800 and 1801 and reassign them so it’s the mean. When we do taxi_modified[:,7].mean() is that computing that on the entire data set? Or is it only doing it for those two rows and how?

[ranklord]

When we do taxi_modified[:,7].mean() is that computing that on the entire data set?

No, it only calculates mean from the values returned by taxi_modified[:,7], i.e. from column 7 across all rows. Then it applies that calculated mean to the values in taxi_modified[1800:1802,7].
Hope it helps.