Essi Shams - 7 months ago 51

Python Question

I have a dataframe called dailyHistogram defined as follows:

`dailyHistogram = pd.DataFrame({'NumVisits':[[0 for x in range(1440)]`

for y in range (180)],

'DoW': [0]*ReportingDateRange.size

}

,columns=['NumVisits','DoF'],

index=ReportingDateRange)

Where NumVisits is a two-dimensional array (1440 by 180) and holds a histogram of some activity in 180 days. DoW is simply a column which holds the day of the week.

The index in this dataframe is the dates on which the activities occurred.

My problem is in performing any operations on dailyHistogram["NumVisits"].

Here's what dailyHistogram["NumVisits"] looks like:

`> dailyHistogram["NumVisits"]`

> Out[193]:

> 2016-01-01 [5, 0, 0, 0, 0,

> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-01-02 [2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-01-03 [6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-01-04 [8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-06-26 [3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-06-27 [4, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...

>

> 2016-06-28 [7, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...

>

> 2016-06-29 [7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> 2016-06-30 [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...

>

> Freq: D, Name: NumVisits, dtype: object

I'd like to sum up all vectors in "NumVisits" for a particular day of the week, but no arithmetic operations seem to be possible on dailyHistogram["NumVisits"]

Answer

That is because `NumVisits`

is a list, and to perform arithmetic on the contents of a list, you need to explicitly apply your functions. For example:

```
df['NumVisits'].apply(sum)
```

For element by element sum in each row:

```
import numpy as np
df['NumVisits'].apply(np.cumsum)
```

For sum across all rows, for each element in row:

```
np.array(dailyHistogram['NumVisits'].tolist()).sum(axis=0)
```

Source (Stackoverflow)