python - Multiple variable derivations in pandas group-by object (time series) -


i have dataframe according spec. below. actual size around 100 million rows, , 150 columns:

df = pd.dataframe({'id' : [1,1,1,1,3,3,3,3]                ,'time_ref' : ['20150401','20150401','20150401','20150401','20150401','20150401','20150401','20150401']                ,'time' : ['20150101', '20150201','20150301','20150401', '20150101',' 20150201','20150301','20150401']                ,'disc' : [3,3,1,1,2,4,5,7]}               ,columns =['id', 'time_ref','time', 'disc' ]              )   time in ['time_ref','time']:     df[time] = pd.to_datetime(df[time]                           ,format = '%y%m%d'                           ,errors = 'ignore')   df

i have solved problem, appearance below:

df2 = pd.dataframe({'id' : [1,1,1,1,3,3,3,3]                ,'time_ref' : ['20150401','20150401','20150401','20150401','20150401','20150401','20150401','20150401']                ,'time' : ['20150101', '20150201','20150301','20150401', '20150101',' 20150201','20150301','20150401']                ,'disc' : [3,3,1,1,2,4,5,7]                ,'disc_agg_diff' : [-2,-2,-2,-2,2,2,2,2]                ,'disc_agg_time_diff' : [2, 2,2 ,2,1,1,1,1]}              ,columns =['id', 'time_ref','time', 'disc', 'disc_agg_diff','disc_agg_time_diff']              )    time in ['time_ref','time']:     df2[time] = pd.to_datetime(df2[time]                           ,format = '%y%m%d'                           ,errors = 'ignore')   df2

  • column disc_agg_diff looks difference between first change in variable disc, i.e. (1-3) = -2 @ time point 20150301 id` = 1. (7-2) = 5 @ time point 20150401 id 3.

  • column disc_agg_time_diff looks @ how many time periods (months) change occurred. id 1, 2 periods. id 3, 1 period.

i getting result lot of groupbys, left joins , numpy.where working way through each ids , monthly data points. problem code big, , if add more variables same derivations becomes bigger , bit messy.

my questions is: can result obtained in clean , efficient manner, code-vise, derivations done (subtractions) can quotes, adding columns, etc. also, speed crucial since data volume big.

many in advance time , considerations!

/swepab

you can use transform. found rather bog post explaining on pbpython.com

something first column

disc_agg_diff

def get_disc_agg_diff(disc_column):     return disc_column.diff().replace(0, none).dropna().iloc[0]

depending on data, using for-loop might more efficient .replace, .dropna , iloc

df.groupby('id')['disc'].transform(get_first_diff)

returns

0   -2 1   -2 2   -2 3   -2 4    2 5    2 6    2 7    2

disc_agg_time_diff

works approximately same `get_first_diff

def get_disc_agg_time_diff(disc_column):     diff = disc_column.diff().reset_index(drop=true)     diff_reduced = diff.replace(0, none).dropna()     return diff_reduced.index[0]

here well, alternative for-loop, works.


Comments

Post a Comment

Popular posts from this blog

angular - Ionic slides - dynamically add slides before and after -

hi i'm using ngfor create set of 3 slides while starting in middle i'm guaranteed able slide left or right on start. when slide right can simple listen reachedend , push slide array i'm looping. but have problem adding slide beginning. if same above , use e.g. array.unshift() or spread add item beginning, view think it's on position 0 , snaps view new slide. the code below work animates slide change index 1. slide = [0,1,2] //example loop slidechanged(event) { if(this.slides.isbeginning()){ this.slide = [this.slide[0]-1, ...this.slide]; this.slides.update(); this.slides.slideto(1) } } <ion-slides [initialslide]="1" (ionslidedidchange)="slidechanged($event)"> <ion-slide *ngfor="let item of slide"> <h1>slide {{item}}</h1> </ion-slide> </ion-slides> any appreciated! you can using ionslidenextend , ionslideprevend events slides . please
Read more

minify - Minimizing css files -

i want know how css files can minimized. currently, using external sites css minifier compress css files. however, after removing whitespaces, comments, etc, file sizes reduced 10-15%. how frameworks bootstrap manage make minimized versions kilobytes. as example, css is: body { background-color: #ff0; } the reduction goes 28 bytes 22 bytes other css files have lot more characters still smaller this. actually minifying code means it's remove thing code white space characters new line characters comments block delimiters it reduces amount of code has transferred on web , speed site load fastly.but unreadable format.
Read more

Add a dynamic header in angular 2 http provider -

i have http interceptor built via tutorial https://scotch.io/@kashyapmukkamala/using-http-interceptor-with-angular2 the problem need have dynamic header changes automatically once changes 'mode' in app. service able tell interceptor change header, or have interceptor pull header (which string)from service each request. able throwing away patch method, call http.patch('new header string') set header string. call in service controls 'mode' setting. wondering if there way interceptor pull recent value service each request or if can add method http provider via interceptor? i've tried call service in interceptor each request returns undefined. because creating new instance of service or copying value before service fired , loaded/changed data. i don't want pass header string every http provider call because defeats purpose of having interceptor, id able set once changes or have provider fetch service before makes request. tl;dr : need add autom
Read more