Pandas extend DataFrame with Zeros

Question

I have following DataFrame which start by an index of 1.10 and increment by 0.05:

          A       B       C       D       E

1.10      3       2       2       1       0
1.15      1       2       0       1       0
1.20      0       0       0       1      -1
1.25      1       1       3      -5       2
1.30     -3       4       2       6       0
...

I want to extend this DataFrame with zeros that the result looks like this:

          A       B       C       D       E

0         0       0       0       0       0
0.05      0       0       0       0       0
0.10      0       0       0       0       0

...

1.10      3       2       2       1       0
1.15      1       2       0       1       0
1.20      0       0       0       1      -1
1.25      1       1       3      -5       2
1.30     -3       4       2       6       0
...

So I want that the index starts by 0 and increments by 0.05 until the original start index of 1.10 is reached. How to do this?

Asked By: Dalon

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Source

Answer 1

Use a reindex with help of numpy.arange:

step = 0.05

out = df.reindex(np.arange(0, df.index.max()+step, step), fill_value=0)

Or if you don’t want to touch the existing DataFrame and only add the missing prior indices (which is more in the spirit of "the index starts by 0 and increments by 0.05 until the original start index of 1.10 is reached"), create the top DataFrame and concat:

step = 0.05

out = pd.concat([pd.DataFrame(0, columns=df.columns,
                              index=np.arange(0, df.index.min(), step)),
                 df])

Output:

      A  B  C  D  E
0.00  0  0  0  0  0
0.05  0  0  0  0  0
0.10  0  0  0  0  0
0.15  0  0  0  0  0
 ...
1.00  0  0  0  0  0
1.05  0  0  0  0  0
1.10  3  2  2  1  0
1.15  0  0  0  0  0
1.20  0  0  0  0  0
1.25  1  1  3 -5  2
1.30 -3  4  2  6  0

Answered By: mozway

Pandas extend DataFrame with Zeros

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