Fitting several regression models with dplyr

Question

I would like to fit a model for each hour(the factor variable) using dplyr, I'm getting an error, and i'm not quite sure what's wrong.

df.h <- data.frame( 
  hour     = factor(rep(1:24, each = 21)),
  price    = runif(504, min = -10, max = 125),
  wind     = runif(504, min = 0, max = 2500),
  temp     = runif(504, min = - 10, max = 25)  
)

df.h <- tbl_df(df.h)
df.h <- group_by(df.h, hour)

group_size(df.h) # checks out, 21 obs. for each factor variable

# different attempts:
reg.models <- do(df.h, formula = price ~ wind + temp)

reg.models <- do(df.h, .f = lm(price ~ wind + temp, data = df.h))

I've tried various variations, but I can't get it to work.

Answer 1

The easiest way to do this, circa May 2015 is to use broom. broom contains three functions that deal with complex returned objects from statistical operations by groups: tidy (which deals with coefficient vectors from statistical operations by groups), glance (which deals with summary statistics from statistical operations by groups), and augment (which deals with observation level results from statistical operations by groups).

Here is a demonstration of its use to extract the various results of linear regression by groups into tidy data_frames.

1. tidy:

   library(dplyr)
   library(broom)
   
   df.h = data.frame( 
     hour     = factor(rep(1:24, each = 21)),
     price    = runif(504, min = -10, max = 125),
     wind     = runif(504, min = 0, max = 2500),
     temp     = runif(504, min = - 10, max = 25)  
   )
   
   dfHour = df.h %>% group_by(hour) %>%
     do(fitHour = lm(price ~ wind + temp, data = .))
   
   # get the coefficients by group in a tidy data_frame
   dfHourCoef = tidy(dfHour, fitHour)
   dfHourCoef
   

   which gives,

       Source: local data frame [72 x 6]
       Groups: hour
   
   hour        term     estimate   std.error  statistic     p.value
   1     1 (Intercept) 53.336069324 21.33190104  2.5002961 0.022294293
   2     1        wind -0.008475175  0.01338668 -0.6331053 0.534626575
   3     1        temp  1.180019541  0.79178607  1.4903262 0.153453756
   4     2 (Intercept) 77.737788772 23.52048754  3.3051096 0.003936651
   5     2        wind -0.008437212  0.01432521 -0.5889765 0.563196358
   6     2        temp -0.731265113  1.00109489 -0.7304653 0.474506855
   7     3 (Intercept) 38.292039924 17.55361626  2.1814331 0.042655670
   8     3        wind  0.005422492  0.01407478  0.3852630 0.704557388
   9     3        temp  0.426765270  0.83672863  0.5100402 0.616220435
   10    4 (Intercept) 30.603119492 21.05059583  1.4537888 0.163219027
   ..  ...         ...          ...         ...        ...         ...
   

2. augment:

    # get the predictions by group in a tidy data_frame
   dfHourPred = augment(dfHour, fitHour)
   dfHourPred
   

   which gives,

   Source: local data frame [504 x 11]
   Groups: hour
   
   hour       price      wind      temp  .fitted  .se.fit     .resid       .hat   .sigma      .cooksd .std.resid
   1     1  83.8414055   67.3780 -6.199231 45.44982 22.42649  38.391590 0.27955950 42.24400 0.1470891067  1.0663820
   2     1   0.3061628 2073.7540 15.134085 53.61916 14.10041 -53.312993 0.11051343 41.43590 0.0735584714 -1.3327207
   3     1  80.3790032  520.5949 24.711938 78.08451 20.03558   2.294497 0.22312869 43.64059 0.0003606305  0.0613746
   4     1 121.9023855 1618.0864 12.382588 54.23420 10.31293  67.668187 0.05911743 40.23212 0.0566557575  1.6447224
   5     1  -0.4039594 1542.8150 -5.544927 33.71732 14.53349 -34.121278 0.11740628 42.74697 0.0325125137 -0.8562896
   6     1  29.8269832  396.6951  6.134694 57.21307 16.04995 -27.386085 0.14318542 43.05124 0.0271028701 -0.6975290
   7     1  -7.1865483 2009.9552 -5.657871 29.62495 16.93769 -36.811497 0.15946292 42.54487 0.0566686969 -0.9466312
   8     1  -7.8548693 2447.7092 22.043029 58.60251 19.94686 -66.457379 0.22115706 39.63999 0.2983443034 -1.7753911
   9     1  94.8736726 1525.3144 24.484066 69.30044 15.93352  25.573234 0.14111563 43.12898 0.0231796755  0.6505701
   10    1  54.4643001 2473.2234 -7.656520 23.34022 21.83043  31.124076 0.26489650 42.74790 0.0879837510  0.8558507
   ..  ...         ...       ...       ...      ...      ...        ...        ...      ...          ...        ...
   

3. glance:

   # get the summary statistics by group in a tidy data_frame
   dfHourSumm = glance(dfHour, fitHour)
   dfHourSumm
   

   which gives,

   Source: local data frame [24 x 12]
   Groups: hour
   
   hour  r.squared adj.r.squared    sigma statistic    p.value df    logLik      AIC      BIC deviance df.residual
   1     1 0.12364561    0.02627290 42.41546 1.2698179 0.30487225  3 -106.8769 221.7538 225.9319 32383.29          18
   2     2 0.03506944   -0.07214506 36.79189 0.3270961 0.72521125  3 -103.8900 215.7799 219.9580 24365.58          18
   3     3 0.02805424   -0.07993974 39.33621 0.2597760 0.77406651  3 -105.2942 218.5884 222.7665 27852.07          18
   4     4 0.17640603    0.08489559 41.37115 1.9277147 0.17434859  3 -106.3534 220.7068 224.8849 30808.30          18
   5     5 0.12575453    0.02861615 42.27865 1.2945915 0.29833246  3 -106.8091 221.6181 225.7962 32174.72          18
   6     6 0.08114417   -0.02095092 35.80062 0.7947901 0.46690268  3 -103.3164 214.6328 218.8109 23070.31          18
   7     7 0.21339168    0.12599076 32.77309 2.4415266 0.11529934  3 -101.4609 210.9218 215.0999 19333.36          18
   8     8 0.21655629    0.12950699 40.92788 2.4877430 0.11119114  3 -106.1272 220.2543 224.4324 30151.65          18
   9     9 0.23388711    0.14876346 35.48431 2.7476160 0.09091487  3 -103.1300 214.2601 218.4381 22664.45          18
   10   10 0.18326177    0.09251307 40.77241 2.0194425 0.16171339  3 -106.0472 220.0945 224.2726 29923.01          18
   ..  ...        ...           ...      ...       ...        ... ..       ...      ...      ...      ...         ...
   

Answer 2

In dplyr 0.4, you can do:

df.h %>% do(model = lm(price ~ wind + temp, data = .))

Answer 3

As of mid 2020, tchakravarty's answer will fail. In order to circumvent the new approach of broom and dpylr seem to interact, the following combination of broom::tidy, broom::augment and broom::glance can be used. We just have to use them inside do() and later unnest() the tibble.

library(dplyr)
library(broom)

df.h = data.frame( 
  hour     = factor(rep(1:24, each = 21)),
  price    = runif(504, min = -10, max = 125),
  wind     = runif(504, min = 0, max = 2500),
  temp     = runif(504, min = - 10, max = 25)  
)

df.h %>% group_by(hour) %>%
  do(fitHour = tidy(lm(price ~ wind + temp, data = .))) %>% 
  unnest(fitHour)
# # A tibble: 72 x 6
#    hour  term        estimate std.error statistic   p.value
#    <fct> <chr>          <dbl>     <dbl>     <dbl>     <dbl>
#  1 1     (Intercept)   82.4     18.1         4.55  0.000248 
#  2 1     wind         -0.0212   0.0108      -1.96  0.0655   
#  3 1     temp         -1.01     0.792       -1.28  0.218    
#  4 2     (Intercept)   25.9     19.7         1.31  0.206    
#  5 2     wind          0.0204   0.0131       1.57  0.135    
#  6 2     temp          0.680    1.01         0.670 0.511    
#  7 3     (Intercept)   88.3     15.5         5.69  0.0000214
#  8 3     wind         -0.0188   0.00998     -1.89  0.0754   
#  9 3     temp         -0.669    0.653       -1.02  0.319    
# 10 4     (Intercept)   73.4     14.2         5.17  0.0000639

df.h %>% group_by(hour) %>%
  do(fitHour = augment(lm(price ~ wind + temp, data = .))) %>% 
  unnest(fitHour)
# # A tibble: 24 x 13
#    hour  r.squared adj.r.squared sigma statistic p.value    df logLik   AIC   BIC deviance
#    <fct>     <dbl>         <dbl> <dbl>     <dbl>   <dbl> <dbl>  <dbl> <dbl> <dbl>    <dbl>
#  1 1        0.246        0.162    39.0     2.93   0.0790     2  -105.  218.  222.   27334.
#  2 2        0.161        0.0674   43.5     1.72   0.207      2  -107.  223.  227.   34029.
#  3 3        0.192        0.102    33.9     2.14   0.147      2  -102.  212.  217.   20739.
#  4 4        0.0960      -0.00445  34.3     0.956  0.403      2  -102.  213.  217.   21169.
#  5 5        0.230        0.144    31.7     2.68   0.0955     2  -101.  210.  214.   18088.
#  6 6        0.0190      -0.0900   39.8     0.174  0.842      2  -106.  219.  223.   28507.
#  7 7        0.0129      -0.0967   37.1     0.118  0.889      2  -104.  216.  220.   24801.
#  8 8        0.197        0.108    35.3     2.21   0.139      2  -103.  214.  218.   22438.
#  9 9        0.0429      -0.0634   39.4     0.403  0.674      2  -105.  219.  223.   27918.
# 10 10       0.0943      -0.00633  35.6     0.937  0.410      2  -103.  214.  219.   22854.
# # … with 14 more rows, and 2 more variables: df.residual <int>, nobs <int>

df.h %>% group_by(hour) %>%
  do(fitHour = glance(lm(price ~ wind + temp, data = .))) %>% 
  unnest(fitHour)
# # A tibble: 504 x 10
#    hour   price  wind   temp .fitted .resid .std.resid   .hat .sigma  .cooksd
#    <fct>  <dbl> <dbl>  <dbl>   <dbl>  <dbl>      <dbl>  <dbl>  <dbl>    <dbl>
#  1 1      94.2   883. -6.64     70.4  23.7       0.652 0.129    39.6 0.0209  
#  2 1      19.3  2107.  2.40     35.4 -16.0      -0.431 0.0864   39.9 0.00584 
#  3 1      60.5  2161. 18.3      18.1  42.5       1.18  0.146    38.5 0.0795  
#  4 1     116.   1244. 12.0      44.0  71.9       1.91  0.0690   35.8 0.0902  
#  5 1     117.   1624. -8.05     56.1  60.6       1.67  0.128    36.9 0.136   
#  6 1      75.0   220. -0.838    78.6  -3.58     -0.101 0.175    40.1 0.000724
#  7 1     106.    765.  6.15     60.0  45.7       1.22  0.0845   38.4 0.0461  
#  8 1      -9.89 2055. 12.3      26.5 -36.4      -0.979 0.0909   39.0 0.0319  
#  9 1      96.1   215. -8.36     86.3   9.82      0.287 0.232    40.0 0.00830 
# 10 1      27.2   323. 22.4      52.9 -25.7      -0.777 0.278    39.4 0.0774  
# # … with 494 more rows

Credits to Bob Muenchen's Blog for inspiration on that.

Answer 4

from the documentation for do:

.f: a function to apply to each piece. The first unnamed argument supplied to .f will be a data frame.

So:

reg.models <- do(df.h, 
                 .f=function(data){
                     lm(price ~ wind + temp, data=data)
                 })

Probably useful to also save which hour the model was fitted for:

reg.models <- do(df.h, 
                 .f=function(data){
                     m <- lm(price ~ wind + temp, data=data)
                     m$hour <- unique(data$hour)
                     m
                 })

Answer 5

I think you can use dplyr in more proper way where you don't need to define function as in @fabians anwser.

results<-df.h %.% 
group_by(hour) %.% 
do(failwith(NULL, lm), formula = price ~ wind + temp)

or

results<-do(group_by(tbl_df(df.h), hour),
failwith(NULL, lm), formula = price ~ wind + temp)

EDIT: Of course it also works without failwith

results<-df.h %.% 
    group_by(hour) %.% 
    do(lm, formula = price ~ wind + temp)


results<-do(group_by(tbl_df(df.h), hour),
lm, formula = price ~ wind + temp)

Answer 6

I believe there's a more compact answer than loki's answer, which abandons the since replaced/superseded do():

library(dplyr)
library(broom)
library(tidyr)

h.lm <- df.h %>%
      nest_by(hour) %>%
      mutate(fitHour = list(lm(price ~ wind + temp, data = data))) %>%
      summarise(tidy_out = list(tidy(fitHour)),
                glance_out = list(glance(fitHour)),
                augment_out = list(augment(fitHour))) %>%
      ungroup()

h.lm
# # A tibble: 24 x 4
#    hour  tidy_out         glance_out        augment_out
#    <fct> <list>           <list>            <list>
#  1 1     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  2 2     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  3 3     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  4 4     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  5 5     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  6 6     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  7 7     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  8 8     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
#  9 9     <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
# 10 10    <tibble [3 × 5]> <tibble [1 × 12]> <tibble [21 × 9]>
# # … with 14 more rows

similar to their answer, in order to access, simply unnest whichever component is desired:

unnest(select(h.lm, hour, tidy_out))
# # A tibble: 72 x 6
#    hour  term        estimate std.error statistic p.value
#    <fct> <chr>          <dbl>     <dbl>     <dbl>   <dbl>
#  1 1     (Intercept) 63.2       20.9        3.02  0.00728
#  2 1     wind        -0.00237    0.0139    -0.171 0.866
#  3 1     temp        -0.266      0.950     -0.280 0.783
#  4 2     (Intercept) 65.1       23.0        2.83  0.0111
#  5 2     wind         0.00691    0.0129     0.535 0.599
#  6 2     temp        -0.448      0.877     -0.510 0.616
#  7 3     (Intercept) 65.2       17.8        3.67  0.00175
#  8 3     wind         0.00515    0.0112     0.458 0.652
#  9 3     temp        -1.87       0.695     -2.69  0.0148
# 10 4     (Intercept) 49.7       17.6        2.83  0.0111
# # … with 62 more rows

Answer 7

As of dplyr 1.0.0, group_split gives a handy shortcut for this action:

library(dplyr)
library(broom)
library(purrr)
df.h <- data.frame( 
  hour     = factor(rep(1:24, each = 21)),
  price    = runif(504, min = -10, max = 125),
  wind     = runif(504, min = 0, max = 2500),
  temp     = runif(504, min = - 10, max = 25)  
)

df.g <- group_split(df.h, hour)
map_dfr(df.g, function(x) tidy(lm(price ~ wind + temp, data=x)))
#> # A tibble: 72 x 5
#>    term        estimate std.error statistic p.value
#>    <chr>          <dbl>     <dbl>     <dbl>   <dbl>
#>  1 (Intercept) -10.4      20.3       -0.512 0.615  
#>  2 wind          0.0377    0.0117     3.23  0.00467
#>  3 temp          1.34      0.890      1.50  0.150  
#>  4 (Intercept)  34.6      18.6        1.86  0.0799 
#>  5 wind          0.0214    0.0125     1.71  0.104  
#>  6 temp          0.332     0.865      0.384 0.706  
#>  7 (Intercept)  42.5      15.3        2.79  0.0122 
#>  8 wind          0.0103    0.0116     0.888 0.386  
#>  9 temp         -0.542     0.736     -0.736 0.471  
#> 10 (Intercept)  64.1      18.8        3.41  0.00312
#> # … with 62 more rows

^{Created on 2021-03-04 by the reprex package (v1.0.0)}