根据其他数据帧从数据帧中选择值

Question

i try to calculate the position of an object based on a timestamp. For this I have two dataframes in pandas. One for the measurement data and one for the position. All the movement is a straightforward acceleration.

Dataframe 1 contains the measurement data:

        ms        force   ...    ...    ...
1      5           20
2      10          20
3      15          25
4      20          30
5      25          20
..... (~ 6000 lines)

Dataframe 2 contains "positioning data"

        ms        speed (m/s)
1      0           0.66
2      4500        0.66
3      8000        1.3
4      16000       3.0
5      20000       3.0
.....(~300 lines)

Now I want to calculate the position of the first dataframe with the data from secound dataframe In Excel I solved the problem by using an array formular but now I have to use Python/Pandas and I cant find a way how to select the correct row from dataframe 2.

My idea is to make something like this: if

In the end I want to display a graph "force <-> way" and not "force <-> time"

Thank you in andvance

========================================================================== Update: In the meantime I could almost solve my issue. Now my Data look like this:

Dataframe 2 (Speed Data):

        pos       v         a         t      t-end    t-start
0    -3.000    0.666667  0.000000  4.500000   4.500000   0.000000
1     0.000    0.666667  0.187037  0.071287   4.571287   4.500000
2     0.048    0.680000  0.650794  0.010244   4.581531   4.571287
3     0.055    0.686667  0.205432  0.064904   4.646435   4.581531
...
15    0.055    0.686667  0.5       0.064904     23.0     20.0
...
28    0.055    0.686667  0.6       0.064904     35.0     34.0
...
30    0.055    0.686667  0.9       0.064904     44.0     39.0

And Dataframe 1 (time based measurement):

        Fx     Fy     Fz      abs_t               expected output ('a' from DF1)
0      -13.9  170.3   45.0   0.005                            0.000000  
1      -14.1  151.6   38.2   0.010                            0.000000  
...
200    -14.1  131.4   30.4   20.015                           0.5
...
300    -14.3  111.9   21.1   34.01                            0.6
...
400    -14.5   95.6   13.2   40.025

So i want to check the time(abs_t) from DF1 and search for the corract 'a' in DF2 So somthing like this (pseudo code):

if (DF1['t_abs'] between (DF2['t-start'], DF2['t-end']):
    DF1['a'] = DF2['a']

I could make two for loops but it looks like the wrong way and is very very slow.

I hope you understand my problem; to provide a running sample is very hard. In Excel I did like this:

Answer 1

I found a very slow solution but atleast its working :(

df1['a'] = 0
for index, row in df2.iterrows():
    start = row['t-start']
    end = row ['t-end']
    a = row ['a']

    df1.loc[(df1['tabs']>start)&(df1['tabs']<end), 'a'] = a