CODEWITHSUNDEEP
pythonpandasdataframe
Andre
Andre

Reputation: 361

how to add a DataFrame to some columns of another DataFrame

I want to add a DataFrame a (containing a loadprofile) to some of the columns of another DataFrame b (also containing one load profile per column). So some columns (load profiles) of b should be overlaid withe the load profile of a.

So lets say my DataFrames look like:

a:

  P[kW]
0   0
1   0
2   0
3   8
4   8
5   0

b:

  P1[kW]  P2[kW] ... Pn[kW]
0   2       2          2
1   3       3          3
2   3       3          3
3   4       4          4
4   2       2          2
5   2       2          2

Now I want to overlay some colums of b:

b.iloc[:, [1]] += a.iloc[:, 0]

I would expect this:

b:

  P1[kW]  P2[kW] ... Pn[kW]
0   2       2          2
1   3       3          3
2   3       3          3
3   4       12         4
4   2       10         2
5   2       2          2

but what I actually get:

b:

  P1[kW]  P2[kW] ... Pn[kW]
0   2       nan        2
1   3       nan        3
2   3       nan        3
3   4       nan        4
4   2       nan        2
5   2       nan        2

That's not exactly what my code and data look like, but the principle is the same as in this abstract example.

Any guesses, what could be the problem?

Many thanks for any help in advance!

EDIT: I actually have to overlay more than one column.
Another example:

load = [0,0,0,0,0,0,0]
data = pd.DataFrame(load)
for i in range(1, 10):
    data[i] = data[0]
data

enter image description here

overlay = pd.DataFrame([0,0,0,0,6,6,0])
overlay

enter image description here

data.iloc[:, [1,2,4,5,7,8]] += overlay.iloc[:, 0]
data

enter image description here

WHAT??! The result is completely crazy. Columns 1 and 2 aren't changed at all. Columns 4 and 5 are changed, but in every row. Columns 7 and 8 are nans. What am I missing?

That is what I would expect the result to look like:

enter image description here

Upvotes: 2

Views: 220

Answers (1)

Utsav
Utsav

Reputation: 5918

Please do not pass the column index '1' of dataframe 'b' as a list but as an element.

Code

b.iloc[:, 1] += a.iloc[:, 0]
b

Output

    P1[kW]  P2[kW]  Pn[kW]
0   2       2       2
1   3       3       3
2   3       3       3
3   4       12      4
4   2       10      2
5   2       2       2

Edit

Seems like this what we are looking for i.e to sum certain columns of data df with overlay df

Two Options

Option 1

cols=[1,2,4,5,7,8]
data[cols] = data[cols] + overlay.values
data

Option 2, if we want to use iloc

cols=[1,2,4,5,7,8]
data[cols] = data.iloc[:,cols] + overlay.iloc[:].values
data

Output

    0   1   2   3   4   5   6   7   8   9
0   0   0   0   0   0   0   0   0   0   0
1   0   0   0   0   0   0   0   0   0   0
2   0   0   0   0   0   0   0   0   0   0
3   0   0   0   0   0   0   0   0   0   0
4   0   6   6   0   6   6   0   6   6   0
5   0   6   6   0   6   6   0   6   6   0
6   0   0   0   0   0   0   0   0   0   0

Upvotes: 1

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