[R] plot factors with dots in R

[Jim Lemon]

Hi Luigi,
Maybe just:

plot(as.numeric(factor(x,levels=x)),y,xaxt="n",
 main="Concentration by effect",
 xlab="Concentration",ylab="Effect")
axis(1,at=1:4,labels=x)

Jim

On Thu, Aug 27, 2020 at 10:16 PM Luigi Marongiu
<marongiu.luigi using gmail.com> wrote:
>
> Hello,
> I have a dataframe as follows:
> ```
> x = c("0 pmol", "10 pmol", "100 pmol", "1000 pmol")
> y = c(0.9306, 1.8906, 2.2396, 2.7917)
> df = data.frame(x, y)
>
> > str(df)
> 'data.frame': 4 obs. of  2 variables:
>  $ x: chr  "0 pmol" "10 pmol" "100 pmol" "1000 pmol"
>  $ y: num  0.931 1.891 2.24 2.792
> ```
> I would like to visualize the data with the classic dots (pch=16) but:
> ```
> > plot(df$y ~ df$x)
> Error in plot.window(...) : need finite 'xlim' values
> In addition: Warning messages:
> 1: In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by coercion
> 2: In min(x) : no non-missing arguments to min; returning Inf
> 3: In max(x) : no non-missing arguments to max; returning -Inf
> ```
> which is right because x is not numeric, so I took the factor:
> ```
> plot(df$y ~ factor(df$x)) # gives bars instead of dots
> plot(df$y ~ factor(df$x), pch = 16) # this also
> ```
> I tried to convert directly the dataframe:
> ```
> df$x = lapply(df$x, factor)
> > str(df)
> 'data.frame': 4 obs. of  2 variables:
>  $ x:List of 4
>   ..$ : Factor w/ 1 level "0 pmol": 1
>   ..$ : Factor w/ 1 level "10 pmol": 1
>   ..$ : Factor w/ 1 level "100 pmol": 1
>   ..$ : Factor w/ 1 level "1000 pmol": 1
>  $ y: num  0.931 1.891 2.24 2.792
>
> > plot(r$y ~ r$x, pch = 16)
> Error in plot.window(...) : need finite 'xlim' values
> In addition: Warning messages:
> 1: In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by coercion
> 2: In min(x) : no non-missing arguments to min; returning Inf
> 3: In max(x) : no non-missing arguments to max; returning -Inf
> ```
> If I try to pass the number of levels:
> ```
> plot(df$y ~ factor(df$x, 1:4), pch = 16) # this draw a boxplot with
> all data on level 1
>
> > df$x = lapply(df$x, factor(1:4))
> Error in match.fun(FUN) :
>   'factor(1:4)' is not a function, character or symbol
> ```
>
> Since the transformation has given only one level (1), my questions are:
> How do I tell R to use a dot instead of a line?
> What is the correct way of setting factors?
>
>
> --
> Best regards,
> Luigi
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.