Calculating a parameter based on values from the previous day-CodePudding

I have a DataFrame which is part of a wider script on Python with the following characteristics:

index dtype='datetime64[ns]', length=365, freq='D'
daily values for different parameters
a default value for DOY 1
a pair of values I previously calculated for some specific dates.

To date, the dataframe structure is something like this:

                 col1    col2      col3       col4       Condition   value to calculate
2018-01-01        5.0  0.853232  0.992774   0.65377        0.0       0.65429
2018-01-02        0.4  0.004652  0.992774   0.65377        0.0       NaN
2018-01-03        0.0  0.000000  0.992774   0.65377        0.0       NaN
2018-01-04        0.0  0.000000  0.992774   0.65377        1.0       0.33456
2018-01-05        0.4  0.004652  0.992774   0.65377        0.0       NaN
              ...       ...       ...       ...        ...       ...

The 'condition' column was used to attribute values at a specific time in the last column

The missing values in the last column should be calculated using data from columns 1 to 4, using values of the previous DOY from both columns 1 to 4 and from the same column of the value that must me calculated.

Also, in case a value is already present at a specific DOY, the formula should reset to start calculation using the previously added value.

I'm not sure how to put this in a loop to execute the operation, or if there are other alternatives to resolve this part of the code I'm working on.

CodePudding user response：

It seems like you need something like this: def compute_value(previous_row, row):

for index, row in df.iterrows():
      if index>0:
           previous_row = df.iloc[index-1]
           row['value to calculate'] = previous_row['col1'] * previous_row['col2'] - previous_row['col3'] * previous_row['col4']

This is how you iterate but not sure to have fully understood the condition and not sure what you meant with, let me know if I can expand

Also, in case a value is already present at a specific DOY, the formula should reset to start calculation using the previously added value.