Tidying methods for multinomial logistic regression models

These methods tidy the coefficients of multinomial logistic regression models generated by multinom of the nnet package.

Usage

# S3 method for multinom
tidy(x, conf.int = FALSE, conf.level = 0.95, exponentiate = FALSE, ...)

Arguments

x

A multinom object returned from nnet::multinom().

conf.int

Logical indicating whether or not to include a confidence interval in the tidied output. Defaults to FALSE.

conf.level

The confidence level to use for the confidence interval if conf.int = TRUE. Must be strictly greater than 0 and less than 1. Defaults to 0.95, which corresponds to a 95 percent confidence interval.

exponentiate

Logical indicating whether or not to exponentiate the the coefficient estimates. This is typical for logistic and multinomial regressions, but a bad idea if there is no log or logit link. Defaults to FALSE.

...

Additional arguments. Not used. Needed to match generic signature only. Cautionary note: Misspelled arguments will be absorbed in ..., where they will be ignored. If the misspelled argument has a default value, the default value will be used. For example, if you pass conf.lvel = 0.9, all computation will proceed using conf.level = 0.95. Two exceptions here are:

tidy() methods will warn when supplied an exponentiate argument if it will be ignored.
augment() methods will warn when supplied a newdata argument if it will be ignored.

Value

A tibble::tibble() with columns:

conf.high: Upper bound on the confidence interval for the estimate.
conf.low: Lower bound on the confidence interval for the estimate.
estimate: The estimated value of the regression term.
p.value: The two-sided p-value associated with the observed statistic.
statistic: The value of a T-statistic to use in a hypothesis that the regression term is non-zero.
std.error: The standard error of the regression term.
term: The name of the regression term.
y.value: The response level.

Examples


# load libraries for models and data
library(nnet)
library(MASS)

example(birthwt)
#> 
#> brthwt> bwt <- with(birthwt, {
#> brthwt+ race <- factor(race, labels = c("white", "black", "other"))
#> brthwt+ ptd <- factor(ptl > 0)
#> brthwt+ ftv <- factor(ftv)
#> brthwt+ levels(ftv)[-(1:2)] <- "2+"
#> brthwt+ data.frame(low = factor(low), age, lwt, race, smoke = (smoke > 0),
#> brthwt+            ptd, ht = (ht > 0), ui = (ui > 0), ftv)
#> brthwt+ })
#> 
#> brthwt> options(contrasts = c("contr.treatment", "contr.poly"))
#> 
#> brthwt> glm(low ~ ., binomial, bwt)
#> 
#> Call:  glm(formula = low ~ ., family = binomial, data = bwt)
#> 
#> Coefficients:
#> (Intercept)          age          lwt    raceblack    raceother  
#>     0.82302     -0.03723     -0.01565      1.19241      0.74068  
#>   smokeTRUE      ptdTRUE       htTRUE       uiTRUE         ftv1  
#>     0.75553      1.34376      1.91317      0.68020     -0.43638  
#>       ftv2+  
#>     0.17901  
#> 
#> Degrees of Freedom: 188 Total (i.e. Null);  178 Residual
#> Null Deviance:	    234.7 
#> Residual Deviance: 195.5 	AIC: 217.5

bwt.mu <- multinom(low ~ ., bwt)
#> # weights:  12 (11 variable)
#> initial  value 131.004817 
#> iter  10 value 98.029803
#> final  value 97.737759 
#> converged

tidy(bwt.mu)
#> # A tibble: 11 × 6
#>    y.level term        estimate std.error statistic p.value
#>    <chr>   <chr>          <dbl>     <dbl>     <dbl>   <dbl>
#>  1 1       (Intercept)   0.823    1.24        0.661 0.508  
#>  2 1       age          -0.0372   0.0387     -0.962 0.336  
#>  3 1       lwt          -0.0157   0.00708    -2.21  0.0271 
#>  4 1       raceblack     1.19     0.536       2.22  0.0261 
#>  5 1       raceother     0.741    0.462       1.60  0.109  
#>  6 1       smokeTRUE     0.756    0.425       1.78  0.0755 
#>  7 1       ptdTRUE       1.34     0.481       2.80  0.00518
#>  8 1       htTRUE        1.91     0.721       2.65  0.00794
#>  9 1       uiTRUE        0.680    0.464       1.46  0.143  
#> 10 1       ftv1         -0.436    0.479      -0.910 0.363  
#> 11 1       ftv2+         0.179    0.456       0.392 0.695  
glance(bwt.mu)
#> # A tibble: 1 × 4
#>     edf deviance   AIC  nobs
#>   <dbl>    <dbl> <dbl> <int>
#> 1    11     195.  217.   189

# or, for output from a multinomial logistic regression
fit.gear <- multinom(gear ~ mpg + factor(am), data = mtcars)
#> # weights:  12 (6 variable)
#> initial  value 35.155593 
#> iter  10 value 14.156582
#> iter  20 value 14.031881
#> iter  30 value 14.025659
#> iter  40 value 14.021414
#> iter  50 value 14.019824
#> iter  60 value 14.019278
#> iter  70 value 14.018601
#> iter  80 value 14.018282
#> iter  80 value 14.018282
#> iter  90 value 14.017126
#> final  value 14.015374 
#> converged
tidy(fit.gear)
#> # A tibble: 6 × 6
#>   y.level term        estimate std.error statistic  p.value
#>   <chr>   <chr>          <dbl>     <dbl>     <dbl>    <dbl>
#> 1 4       (Intercept)  -11.2       5.32     -2.10  3.60e- 2
#> 2 4       mpg            0.525     0.268     1.96  5.02e- 2
#> 3 4       factor(am)1   11.9      66.9       0.178 8.59e- 1
#> 4 5       (Intercept)  -18.4      67.9      -0.271 7.87e- 1
#> 5 5       mpg            0.366     0.292     1.25  2.10e- 1
#> 6 5       factor(am)1   22.4       2.17     10.3   4.54e-25
glance(fit.gear)
#> # A tibble: 1 × 4
#>     edf deviance   AIC  nobs
#>   <dbl>    <dbl> <dbl> <int>
#> 1     6     28.0  40.0    32

Tidying methods for multinomial logistic regression models

Usage

Arguments

See also

Value

Examples