# effects.mlogit: Marginal effects of the covariates In mlogit: multinomial logit model

## Description

The `effects` method for `mlogit` objects computes the marginal effects of the selected covariate on the probabilities of choosing the alternatives

## Usage

 ```1 2 3``` ```## S3 method for class 'mlogit' effects(object, covariate = NULL, type = c("aa", "ar", "rr", "ra"), data = NULL, ...) ```

## Arguments

 `object` a `mlogit` object, `covariate` the name of the covariate for which the effect should be computed, `type` the effect is a ratio of two marginal variations of the probability and of the covariate ; these variations can be absolute `"a"` or relative `"r"`. This argument is a string that contains two letters, the first refers to the probability, the second to the covariate, `data` a data.frame containing the values for which the effects should be calculated. The number of lines of this data.frame should be equal to the number of alternatives, `...` further arguments.

## Value

If the covariate is alternative specific, a \$J\$ times \$J\$ matrix is returned, \$J\$ being the number of alternatives. Each line contains the marginal effects of the covariate of one alternative on the probability to choose any alternative. If the covariate is individual specific, a vector of length \$J\$ is returned.

## Author(s)

Yves Croissant

`mlogit` for the estimation of multinomial logit models.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```data("Fishing", package = "mlogit") Fish <- mlogit.data(Fishing, varying = c(2:9), shape = "wide", choice = "mode") m <- mlogit(mode ~ price | income | catch, data = Fish) # compute a data.frame containing the mean value of the covariates in # the sample z <- with(Fish, data.frame(price = tapply(price, index(m)\$alt, mean), catch = tapply(catch, index(m)\$alt, mean), income = mean(income))) # compute the marginal effects (the second one is an elasticity effects(m, covariate = "income", data = z) effects(m, covariate = "price", type = "rr", data = z) effects(m, covariate = "catch", type = "ar", data = z) ```

### Example output

```Loading required package: Formula

Please cite the 'maxLik' package as:
Henningsen, Arne and Toomet, Ott (2011). maxLik: A package for maximum likelihood estimation in R. Computational Statistics 26(3), 443-458. DOI 10.1007/s00180-010-0217-1.

If you have questions, suggestions, or comments regarding the 'maxLik' package, please use a forum or 'tracker' at maxLik's R-Forge site:
https://r-forge.r-project.org/projects/maxlik/
beach          boat       charter          pier
1.132965e-06  3.113068e-05 -2.408677e-05 -8.176877e-06
beach       boat    charter       pier
beach   -2.4634447  0.1512128  0.1512128  0.1512128
boat     0.5797049 -0.8172610  0.5797049  0.5797049
charter  0.9741351  0.9741351 -1.1590941  0.9741351
pier     0.1844507  0.1844507  0.1844507 -2.4302068
beach        boat     charter         pier
beach    0.040943135 -0.01803326 -0.01984425 -0.003065622
boat    -0.010447074  0.10568073 -0.08249023 -0.012743428
charter -0.012623645 -0.09057996  0.11860203 -0.015398428
pier    -0.001887074 -0.01354055 -0.01490036  0.030327981
```

mlogit documentation built on Feb. 2, 2018, 3:01 p.m.