# How to create two indicator variables using two specific observations in a dataset in RStudio

Hi, and welcome!

Please see the FAQ: What's a reproducible example (`reprex`) and how do I do one? Using a reprex, complete with representative data will attract quicker and more answers. Also, please see the homework policy.

Let's use the built-in `mtcars` dataset to show how this is done. We are going to see how mpg, as a response variable is affected by two other variables and the independent variables. The pieces are the data, `mtcars`, the `mpg` (miles per gallon) `wt` (vehicle weight) and `drat` (rear axle ratio) and the function `lm` and the values (result) object to capture the calculation.

``````fit <- lm(mpg ~ wt + drat, data = mtcars)
summary(fit)
#>
#> Call:
#> lm(formula = mpg ~ wt + drat, data = mtcars)
#>
#> Residuals:
#>     Min      1Q  Median      3Q     Max
#> -5.4159 -2.0452  0.0136  1.7704  6.7466
#>
#> Coefficients:
#>             Estimate Std. Error t value Pr(>|t|)
#> (Intercept)   30.290      7.318   4.139 0.000274 ***
#> wt            -4.783      0.797  -6.001 1.59e-06 ***
#> drat           1.442      1.459   0.989 0.330854
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#>
#> Residual standard error: 3.047 on 29 degrees of freedom
#> Multiple R-squared:  0.7609, Adjusted R-squared:  0.7444
#> F-statistic: 46.14 on 2 and 29 DF,  p-value: 9.761e-10
``````

Created on 2020-04-06 by the reprex package (v0.3.0)

The choice of `mpg` on the left hand side of the \sim and `wt` and `drat` on the right hand is based on the design of the analysis. There's no right or wrong answer.