python - How do I put a series (such as) the result of a pandas groupby.apply(f) into a new column of the dataframe? -


i have dataframe, want calculate statitics on (value_count, mode, mean, etc.) , put result in new column. current solution o(n**2) or so, , i'm sure there faster, obvious method i'm overlooking.

import pandas pd import numpy np  df = pd.dataframe(np.random.randint(10, size=(100, 10)),                     columns = list('abcdefghij'))  df['result'] = 0  groups = df.groupby([df.i, df.j]) g in groups:     icol_eq = df.i == g[0][0]     jcol_eq = df.j == g[0][1]     i_and_j = icol_eq & jcol_eq     df['result'][i_and_j] = len(g[1])

the above works, extremely slow large dataframes.

i tried

df['result'] = df.groupby([df.i, df.j]).apply(len)

but doesn't seem work.

nor does

def f(g):     g['result'] = len(g)     return g  df.groupby([df.i, df.j]).apply(f)

nor can merge resulting series of df.groupby.apply(lambda x: len(x))

you want use transform:

in [98]:  df['result'] = df.groupby([df.i, df.j]).transform(len) df out[98]:      b  c  d  e  f  g  h   j  result 0   6  1  3  0  1  1  4  2  8  6       6 1   1  3  9  7  5  5  3  5  4  4       1 2   1  5  0  1  8  1  4  7  3  9       1 3   6  8  6  4  6  0  8  0  6  5       6 4   7  9  7  2  8  9  9  6  0  6       7 5   3  5  5  7  2  7  7  3  2  8       3 6   5  0  4  7  5  7  5  7  9  1       5 7   3  2  5  4  3  6  8  4  2  0       3 8   2  3  0  4  8  5  7  9  7  2       2 9   1  1  3  2  3  5  6  6  5  6       1 10  3  0  2  7  1  8  1  3  5  4       3 ....

transform returns series index aligned original df can add column


Comments

Post a Comment

Popular posts from this blog

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

php - Nothing but 'run(); ' when browsing to my local project, how do I fix this? -

i added new project. made mistake in projectname.conf file in sites-available apache2, led me reinstalling apache2. after reinstalling , re-enabling projects on every page of every project .. <body> run(); </body> .. i've run composer update, restarted service, restarted pc, checked config files, tried disabling new project. there nothing in error log, , access.log: 127.0.0.1 - - [15/may/2015:01:40:47 +0200] "get / http/1.1" 304 181 "-" "mozilla/5.0 (x11; ubuntu; linux x86_64; rv:38.0) gecko/20100101 firefox/38.0" maybe i'm forgetting apache2 reinstall? don't think did different last time installed it. looks haven't setup php correctly. take @ this great guide , maybe you're forgetting link php config apache2.
Read more

php - How can I echo out this array? -

i don't know how go grabbing data in variable , put foreach loop. class tree{ private $info = array( array('name'=>'jim','state'=>'nu','company'=>'nu','phone'=>array('cell'=>'5615111111','office'=>'5611111111'),'email'=>array('primary'=>'exs@example.com','ex@there.com')), array('name'=>'joe smith','city'=>'phoenix','phone'=>'4805551111','email'=>'jsmith@some_email.com'), array('name'=>'john doe','city'=>'chandler','company'=>'doe co.','email'=>array('jdoe@gmail.com','personal'=>'email@email.com'),'phone'=>'6025550002') ); } if you're inside of class, can access private variable using $this->variablename . example, i...
Read more