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.

Ha

```
library(tidyverse)
library(Hmisc)
#> 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
library(cowplot)
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]
return(n)
}
df = data.frame(p1=seq(0.1,0.8, 0.05),
rr = 0.33)
df = df %>%
rowwise() %>%
mutate(n=f.tmp(p1))
head(df)
#> # 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)) +
geom_point()+
geom_line(col='red')+
ggtitle('Red line from a data frame')
tmpplot1 = ggplot(df, aes(x=p1, y=n)) +
geom_point(alpha=.2)+
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)}

DavoWW
February 7, 2021, 7:57am
3
Hi @Wobniar ,
You were on the right track.
`help(Vectorize)`

So, this works:

```
geom_point(alpha=.2)+
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.

Best.

Ha

system
Closed
February 28, 2021, 4:44pm
5
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