# [R] [External] add equation and rsqared to plot

Richard M. Heiberger rmh @end|ng |rom temp|e@edu
Wed Apr 6 22:36:28 CEST 2022

```I think you are looking for atop(a,b)
See ? plotmath

> On Apr 06, 2022, at 15:58, PIKAL Petr <petr.pikal using precheza.cz> wrote:
>
> Dear all
>
>
> I want to add equation and rsquared values to plot and I am lost in correct expression form. I want to have 2 lines, one with equation and one with r squared values.
>
>
> Here is what I made.
>
> # function to extract values from lm fit.
>
>
> lm_eqn = function(m) {
>  l <- list(a = format(coef(m)[1], digits = 4),
>      b = format(abs(coef(m)[2]), digits = 4),
>      r2 = format(summary(m)\$r.squared, digits = 3),
>  if (coef(m)[2] >= 0)  {
>    eq <- substitute(italic(y) == a + b %.% italic(x), l)
>  } else {
>    eq <- substitute(italic(y) == a - b %.% italic(x),l)
>
>  }
>  expression(atop(eq, req))
> }
>
>
> #Example
>
> x <- 1:10
> y <- x*5 +rnorm(10)
> plot(x,y)
> fit <- lm(y~x)
> text(4,40, lm_eqn(fit))
>
>
> I know that both eq and req are correct expressions and when the last line in function is either eq or req, the example gives correct result.
>
>
> But how to get both expressions one above the other is mystery.
>
>
>
> Best regards.
>
> Petr
>
>
>
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