Set DateTime to index and then sum over a day - pandas

i would like to change the index of my dataframe to datetime to sum the colum "Heizung" over a day.
But it dont work.
After i set the new index, i like to use resample to sum over a day.
Here is an extraction from my dataframe.
Nr;DatumZeit;Erdtemp;Heizung
0;25.04.21 12:58:42;21.8;1
1;25.04.21 12:58:54;21.8;1
2;25.04.21 12:59:06;21.9;1
3;25.04.21 12:59:18;21.9;1
4;25.04.21 12:59:29;21.9;1
5;25.04.21 12:59:41;22.0;1
6;25.04.21 12:59:53;22.0;1
7;25.04.21 13:00:05;22.1;1
8;25.04.21 13:00:16;22.1;0
9;25.04.21 13:00:28;22.1;0
10;25.04.21 13:00:40;22.1;0
11;25.04.21 13:00:52;22.2;0
12;25.04.21 13:01:03;22.2;0
13;25.04.21 13:01:15;22.2;1
14;25.04.21 13:01:27;22.2;1
15;25.04.21 13:01:39;22.3;1
16;25.04.21 13:01:50;22.3;1
17;25.04.21 13:02:02;22.4;1
18;25.04.21 13:02:14;22.4;1
19;25.04.21 13:02:26;22.4;0
20;25.04.21 13:02:37;22.4;1
21;25.04.21 13:02:49;22.4;0
22;25.04.21 13:03:01;22.4;0
23;25.04.21 13:03:13;22.5;0
24;25.04.21 13:03:25;22.4;0
This is my code
import pandas as pd
Tab = pd.read_csv('/home/kai/Dokumente/TempData', delimiter=';')
Tab1 = Tab[["DatumZeit","Erdtemp","Heizung"]].copy()
Tab1['DatumZeit'] = pd.to_datetime(Tab1['DatumZeit'])
Tab1.plot(x='DatumZeit', figsize=(20, 5),subplots=True)
#Tab1.index.to_datetime()
#Tab1.index = pd.to_datetime(Tab1.index)
Tab1.set_index('DatumZeit')
Tab.info()
Tab1.resample('D').sum()
print(Tab1.head(10))

This is how we can set index and create Timestamp object and then resample it for 'D' and sum a column over it.
Tab1['DatumZeit'] = pd.to_datetime(Tab1.DatumZeit)
Tab1 = Tab1.set_index('DatumZeit') ## missed here
Tab1.resample('D').Heizung.sum()
If we don't want to set index explicitly then other way to resample is pd.Grouper.
Tab1['DatumZeit'] = pd.to_datetime(Tab1.DatumZeit
Tab1.groupby(pd.Grouper(key='DatumZeit', freq='D')).Heizung.sum()
If we want output to be dataframe, then we can use to_frame method.
Tab1 = Tab1.groupby(pd.Grouper(key='DatumZeit', freq='D')).Heizung.sum().to_frame()
Output
Heizung
DatumZeit
2021-04-25 15

Pivot tables to the rescue:
import pandas as pd
import numpy as np
Tab1.pivot_table(index=["DatumZeit"], values=["Heizung"], aggfunc=np.sum)
If you need to do it with setting the index first, you need to use inplace=True on set_index
Tab1.set_index("DatumZeit", inplace=True)
Just note if you do this way, you can't go back to a pivot table. In the end, it's whatever works best for you.

Related

How to categorize a range of hours in Pandas?

In my project I am trying to create a new column to categorize records by range of hours, let me explain, I have a column in the dataframe called 'TowedTime' with time series data, I want another column to categorize by full hour without minutes, for example if the value in the 'TowedTime' column is 09:32:10 I want it to be categorized as 9 AM, if says 12:45:10 it should be categorized as 12 PM and so on with all the other values. I've read about the .cut and bins function but I can't get the result I want.
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import datetime
df = pd.read_excel("Baltimore Towing Division.xlsx",sheet_name="TowingData")
df['Month'] = pd.DatetimeIndex(df['TowedDate']).strftime("%b")
df['Week day'] = pd.DatetimeIndex(df['TowedDate']).strftime("%a")
monthOrder = ['Jan', 'Feb', 'Mar', 'Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec']
dayOrder = ['Mon','Tue','Wed','Thu','Fri','Sat','Sun']
pivotHours = pd.pivot_table(df, values='TowedDate',index='TowedTime',
columns='Week day',
fill_value=0,
aggfunc= 'count',
margins = False, margins_name='Total').reindex(dayOrder,axis=1)
print(pivotHours)
First, make sure the type of the column 'TowedTime' is datetime. Second, you can easily extract the hour from this data type.
df['TowedTime'] = pd.to_datetime(df['TowedTime'],format='%H:%M:%S')
df['hour'] = df['TowedTime'].dt.hour
hope it answers your question
With the help of #Fabien C I was able to solve the problem.
First, I had to check the data type of values in the 'TowedTime' column with dtypes function. I found that were a Object.
I proceed to try convert 'TowedTime' to datetime:
df['TowedTime'] = pd.to_datetime(df['TowedTime'],format='%H:%M:%S').dt.time
Then to create a new column in the df, for only the hours:
df['Hour'] = pd.to_datetime(df['TowedTime'],format='%H:%M:%S').dt.hour
And the result was this:
You can notice in the image that 'TowedTime' column remains as an object, but the new 'Hour' column correctly returns the hour value.
Originally, the dataset already had the date and time separated into different columns, I think they used some method to separate date and time in excel and this created the time ('TowedTime') to be an object, I could not convert it, Or at least that's what the dtypes function shows me.
I tried all this Pandas methods for converting the Object to Datetime :
df['TowedTime'] = pd.to_datetime(df['TowedTime'])
df['TowedTime'] = pd.to_datetime(df['TowedTime'])
df['TowedTime'] = df['TowedTime'].astype('datetime64[ns]')
df['TowedTime'] = pd.to_datetime(df['TowedTime'], format='%H:%M:%S')
df['TowedTime'] = pd.to_datetime(df['TowedTime'], format='%H:%M:%S')

How can I add values from pandas group to new Dataframe after a function?

I am trying to separate a Dataframe into groups, run each group through a function, and have the return value from the first row of each group placed into a new Dataframe.
When I try the code below, I can print out the information I want, but when I try to add it to the new Dataframe, it only shows the values for the last group.
How can I add the values from each group into the new Dataframe?
Thanks,
Here is what I have so far:
import pandas as pd
import numpy as np
#Build random dataframe
df = pd.DataFrame(np.random.randint(0,40,size=10),
columns=["Random"],
index=pd.date_range("20200101", freq='6h',periods=10))
df["Random2"] = np.random.randint(70,100,size=10)
df["Random3"] = 2
df.index =df.index.map(lambda t: t.strftime('%Y-%m-%d'))
df.index.name = 'Date'
df.reset_index(inplace=True)
#Setup groups by date
df = df.groupby(['Date']).apply(lambda x: x.reset_index())
df.drop(["index","Date"],axis=1,inplace = True)
#Creat new dataframe for newValue
df2 = pd.DataFrame(index=(df.index)).unstack()
#random function for an example
def any_func(df):
df["Value"] = df["Random"] * df["Random2"] / df["Random3"]
return df["Value"]
#loop by unique group name
for date in df.index.get_level_values('Date').unique():
#I can print the data I want
print(any_func(df.loc[date])[0])
#But when I add it to a new dataframe, it only shows the value from the last group
df2["newValue"] = any_func(df.loc[date])[0]
df2
Unrelated, but try modifying your any_func to take advantage of vectorized functions is possible.
Now if I understand you correctly:
new_value = df['Random'] * df['Random2'] / df['Random3']
df2['New Value'] = new_value.loc[:, 0]
This line of code gave me the desired outcome. I just needed to set the index using the "date" variable when I created the column, not when I created the Dataframe.
df2.loc[date, "newValue"] = any_func(df.loc[date])[0]

How to access dask dataframe index value in map_paritions?

I am trying to use dask dataframe map_partition to apply a function which access the value in the dataframe index, rowise and create a new column.
Below is the code I tried.
import dask.dataframe as dd
import pandas as pd
df = pd.DataFrame(index = ["row0" , "row1","row2","row3","row4"])
df
ddf = dd.from_pandas(df, npartitions=2)
res = ddf.map_partitions(lambda df: df.assign(index_copy= str(df.index)),meta={'index_copy': 'U' })
res.compute()
I am expecting df.index to be the value in the row index, not the entire partition index which it seems to refer to. From the doc here, this work well for columns but not the index.
what you want to do is this
df.index = ['row'+str(x) for x in df.index]
and for that first create your pandas dataframe and then run this code after you will have your expected result.
let me know if this works for you.

Upsampling datetime - ValueError: cannot reindex a non-unique index with a method or limit

I get the error below when I try to upsample...
import pandas as pd
from datetime import date
df1=pd.read_csv("C:/Codes/test.csv")
df1['Date'] = pd.to_datetime(df1['Date'])
df1 = df1.set_index(['Date'])
df2 = pd.DataFrame()
df2 = df1.Gen.resample('H').ffill()
I get this error...ValueError: cannot reindex a non-unique index with a method or limit. Please advise.
My test.csv is a simple file with two columns containing these 5 records
Date|Gen
----|----
5/1/2017|Ggulf
5/2/2017|Ggulf
5/1/2017|Nelson
5/3/2017|Ggulf
5/4/2017|Nelson
An index needs to have unique values. Your first record and third record have the same date '5/1/2017' which makes it impossible to set the date column as an index column.

pandas HDFStore select rows with non-null values in the data column

In pandas Dataframe/Series there's a .isnull() method. Is there something similar in the syntax of where= filter of the select method of HDFStore?
WORKAROUND SOLUTION:
The /meta section of a data column inside hdf5 can be used as a hack solution:
import pandas as pd
store = pd.HDFStore('store.h5')
print(store.groups)
non_null = list(store.select("/df/meta/my_data_column/meta"))
df = store.select('df', where='my_data_column == non_null')