Stata package for finding argmax and argmin

Installing

You can clone the Git repo with

git clone https://github.com/jrfiedler/stata_argmax

Or you can download a zip archive by clicking on the "Download ZIP" button on the right side of this page.

Syntax

argmax varname [if] [in] [, options]

argmin varname [if] [in] [, options]

options:

1. by(varlist)

• group by specified variables when finding values; the values will be calculated separately in each group implied by varlist

2. eval(varlist)

• evaluate specified variables at returned observation number(s)

Description

argmax/argmin finds the observation number of the max/min value of the given numeric variable varname. Missing values are excluded. If the max/min value occurs in multiple observations, then argmax/argmin finds all such observations. If the option eval(varlist) is specified, then argmax/argmin also returns the values of these variables at the calculated observation numbers. If by(varlist) is specified, then argmax/argmin does the above for each group implied by these variables (excluding missing values).

Max/min values and observation numbers are put in return matrix r(values), along with any by and eval variables. If any of the by variables are string, their values will be replaced by integer values in the r(values) matrix. If any of the eval variables are string, their values will be the missing value "." in the r(values) matrix.

Example usage

. sysuse auto
(1978 Automobile Data)

. argmax price

. matrix list r(values)

r(values)[1,2]
    obs_num    price
r1       13    15906

. argmax price , eval(rep78)

. matrix list r(values)

r(values)[1,3]
    obs_num    price    rep78
r1       13    15906        3

. argmax price , by(rep78)

. matrix list r(values)

r(values)[5,3]
    obs_num    price    rep78
r1       48     4934        1
r2       12    14500        2
r3       13    15906        3
r4       55     9735        4
r5       74    11995        5

. argmax price , by(rep78) eval(mpg)

. matrix list r(values)

r(values)[5,4]
    obs_num    price    rep78      mpg
r1       48     4934        1       18
r2       12    14500        2       14
r3       13    15906        3       21
r4       55     9735        4       25
r5       74    11995        5       17

Author

James Fiedler (jrfiedler at gmail dot com)