Pandas Vectorized Methods - Intro to Data Science

• 0:02 - 0:06
Also allows you operate on your data frame in a vectorized and item by item way.
• 0:07 - 0:09
What does it mean to operate on data frame in a vectorized way?
• 0:10 - 0:12
Let's say we have the following data frame.
• 0:12 - 0:15
This data frame has 2 columns, 1 and 2.
• 0:17 - 0:19
And 4 rows, a, b, c, and d.
• 0:21 - 0:23
All of the values are integers.
• 0:23 - 0:24
We can call data frame that apply and
• 0:24 - 0:27
provide us the argument sum arbitrary function.
• 0:27 - 0:28
In this case,
• 0:28 - 0:33
numpy.mean to perform that function on the vector that is every single column.
• 0:33 - 0:36
So when we call df.apply numpy.mean.
• 0:36 - 0:39
What we get back is the mean of every single column in df.
• 0:39 - 0:41
This is itself a new data frame.
• 0:41 - 0:45
There are also some operations that simply cannot be vectorized in this way.
• 0:45 - 0:48
That is, take an numpy array as their input and
• 0:48 - 0:50
then return another array or value.
• 0:51 - 0:54
We can also, in this case, call map on particular columns.
• 0:54 - 0:56
Or apply map on entire data frames.
• 0:58 - 1:01
These methods will accept functions that take in a single value, and
• 1:01 - 1:03
return a single value.
• 1:03 - 1:08
For example let's say that we said df one.map lambda x x greater than or
• 1:08 - 1:09
equal to 1.
• 1:09 - 1:13
What this does is goes through every single value in the 1 column, and
• 1:13 - 1:17
evaluates whether or not that value is greater than or equal to 1.
• 1:17 - 1:24
If we were to call df.applymap lambda x x greater than or equal to 1.
• 1:24 - 1:28
The same function is evaluated over every single value in the data frame.
• 1:28 - 1:30
As opposed to just the "one" column.
タイトル：
Pandas Vectorized Methods - Intro to Data Science

more » « less
Video Language:
English
Team:
Udacity
プロジェクト：
ud359: Intro to Data Science
Duration:
01:32
 Udacity Robot edited English (United States) subtitles for 01-20 Pandas Vectorized Methods

English (United States) subtitles

改訂

• API
Udacity Robot