[FIXED] getting error trying to compare values in a row using pandas

Issue

given a data set such as: link to data: I want to compare and find the maximas of the avg glucose, and once I find the maximas I want to be able to compute the rate of glucose utilization

The error occurs when I write

if(df1['Avg. Glucose (mg/dL)'][i] > df1['Avg. Glucose (mg/dL)'][i + 1]):

in :

import pandas as pd

# reading sheet 1
df = pd.read_excel('data.xlsx', sheet_name=1)

# removing all rows with null Avg Glucose values and putting it into new data frame
df1 = df.dropna(subset=["Avg. Glucose (mg/dL)"])

# iterrating through the rows of new data frame
for i in df1.index:
    # after day 10
    if(df1['Days of Culture'][i] > 10): 
        #if the value is greater than the next
        if(df1['Avg. Glucose (mg/dL)'][i] > df1['Avg. Glucose (mg/dL)'][i + 1]):
            print(df1['Avg. Glucose (mg/dL)'][i])

Getting this error:

Traceback (most recent call last):
  File "C:\Users\Abrar Mahi\AppData\Local\Programs\Python\Python38\lib\site-packages\pandas\core\indexes\base.py", line 3080, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas\_libs\index.pyx", line 70, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 101, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 1625, in pandas._libs.hashtable.Int64HashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 1632, in pandas._libs.hashtable.Int64HashTable.get_item
KeyError: 13

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:/Users/Abrar Mahi/Desktop/Biomilq/BioMilq.py", line 14, in <module>
    if(df1['Avg. Glucose (mg/dL)'][i] > df1['Avg. Glucose (mg/dL)'][i + 1]):
  File "C:\Users\Abrar Mahi\AppData\Local\Programs\Python\Python38\lib\site-packages\pandas\core\series.py", line 853, in __getitem__  
    return self._get_value(key)
  File "C:\Users\Abrar Mahi\AppData\Local\Programs\Python\Python38\lib\site-packages\pandas\core\series.py", line 961, in _get_value   
    loc = self.index.get_loc(label)
  File "C:\Users\Abrar Mahi\AppData\Local\Programs\Python\Python38\lib\site-packages\pandas\core\indexes\base.py", line 3082, in get_loc
    raise KeyError(key) from err
KeyError: 13

my goal is to find the rate of change of the avg glucose

Solution

(forgot to post my solution, hence late update) This is what I did to find the difference of days in order to calculate the rate of change:

#finding the difference in days from each day of glucose monitoring
df1['new'] = df1['Days of Culture'].diff()

# creating a new column which trackes the daily loss in glucose
df1['Daily change in Glucose (mg/dL)'] = df1['Rate'] / df1['new'] 

Answered By - abrar mahi