Plotting function with geom_function

I need some help with plotting a function with geom_function.

I want to plot, for different risk ratio RR, the sample size n1 vs the proportion p1 for a two proportions test. I modify the function hmisc::bsamsize as below and want to use geom_function to plot the curve.

The problem is that I got a horizontal line instead of the red curve (on the right hand side). I think the problem is that f.test function is not vectorized. What is the correct way to do it?

Thanks in advance.

Ha Nguyen

I am sorry, wrong pasting.


#> Loading required package: lattice
#> Loading required package: survival
#> Loading required package: Formula
#> Attaching package: 'Hmisc'
#> The following objects are masked from 'package:dplyr':
#>     src, summarize
#> The following objects are masked from 'package:base':
#>     format.pval, units

f.tmp = function(p1_, rr_=0.33, alpha_=0.05, power_=0.9){
    # Calculating the sample size to test p1 vs rr*p1 with hmisc::bsamsize
    # Note that hmisc::bsamsize returns a vector of size 2 and f.tmp returns the first elelement
    n = bsamsize(p1_, rr_*p1_, alpha=alpha_, power=power_)[1] 

df = data.frame(p1=seq(0.1,0.8, 0.05),
                rr = 0.33)
df = df %>%
  rowwise() %>%

#> # A tibble: 6 x 3
#> # Rowwise: 
#>      p1    rr     n
#>   <dbl> <dbl> <dbl>
#> 1  0.1   0.33 289. 
#> 2  0.15  0.33 185. 
#> 3  0.2   0.33 133. 
#> 4  0.25  0.33 102. 
#> 5  0.3   0.33  81.0
#> 6  0.35  0.33  66.1

tmpplot2 = ggplot(df, aes(x=p1, y=n)) + 
  ggtitle('Red line from a data frame')

tmpplot1 = ggplot(df, aes(x=p1, y=n)) +
  geom_function(fun="f.tmp", color='red')+
  ggtitle('Red line from geom_function')

plot_grid(tmpplot1, tmpplot2)

Created on 2021-02-06 by the reprex package (v0.3.0)

Hi @Wobniar,
You were on the right track.

So, this works:

  geom_function(fun=Vectorize("f.tmp"), color='red')+
  ggtitle('Red line from geom_function')

Hi @DavoWW, thank you very much. I am not aware of the function Vectorize and learn about an useful one today.



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