[R] Problems with facets in ggplot2

[Rui Barradas]

Às 11:08 de 04/08/2023, Nick Wray escreveu:
> Hello  I am wrestling with ggplot – I have produced a facetted plot of
> flows under various metrics but I can’t find info on the net which tells me
> how to do three things
> 
> 
> I have created some simplified mock data to illustrate (and using a
> colour-blind palette):
> 
> 
> library(ggplot2)
> 
> library(forcats)
> 
> cb8<- c("#000000", "#E69F00", "#56B4E9", "#009E73","#F0E442", "#0072B2",
> "#D55E00", "#CC79A7")
> 
> set.seed<-(040823)
> 
>    mock<- set.seed<-(040823)
> 
> 
> mock<-as.data.frame(cbind(rep((1990:1995),8),round(rnorm(48,50,10),3),rep(c(rep("Tweed",6),rep("Tay",6)),4),rep(c("AMAX","Mean","AMIN","Median"),each=12)))
> 
>    colnames(mock)<-c("Year","Flow","Stat","Metric")
> 
>    mock
> 
> 
> 
>    ggplot(mock, aes(Year,Flow, group = factor(Stat), colour = factor(Stat)))+
> 
>      coord_cartesian(ylim = c(0, 100)) +
> 
>      geom_line(size=1)+
> 
>      scale_color_manual(name = "Stat", values = cb8[4:7])+
> 
>      scale_y_discrete(breaks=c(0,25,50,75,100),labels=c(0,25,50,75,100))+
> 
>      facet_wrap(vars(Metric),nrow=2,ncol=2)+
> 
>      ylab("Flow")
> 
> 
> 
> 1)This gives me a facetted plot but I can’t work out why I’m not getting a
> labelled y scale
> 
> 
> 
> 2)Why are plots down at the bottom of the facets rather than in the middle?
> 
> 
> 
> 3)And also I’d like the plots to be in the order (top left to bottom right)
> of
> 
> AMAX MEAN AMIN MEDIAN
> 
> but if I add in the line
> facet_grid(~fct_relevel(Metric,"AMAX","Mean","AMIN","Median")) before the
> line ylab it disrupts the 2x2 layout
> 
> 
> 
> Can anyone tell me how to resolve these problems?  Thanks Nick Wray
> 
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> 
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Hello,

The main problem is the way ou create the data set. cbind defaults to 
creating a matrix and since some of the vectors are of class "character" 
all others will be coerced to character too. And Year and Flow will no 
longer be numeric.

You can coerce those two columns to numeric manually or you can use 
data.frame(), not as.data.frame(), to create the data set.
And you were, therefore, using scale_y_discrete when it should be 
scale_y_continuous. Corrected below.

As for the relevel, I'm not getting any errors.



library(ggplot2)
library(forcats)

cb8<- c("#000000", "#E69F00", "#56B4E9", "#009E73",
         "#F0E442", "#0072B2", "#D55E00", "#CC79A7")

set.seed(040823)

# the right way of creating the data set
mock <- data.frame(
   Year = rep((1990:1995),8),
   Flow = round(rnorm(48,50,10),3),
   Stat = rep(c(rep("Tweed",6), rep("Tay",6)),4),
   Metric = rep(c("AMAX","Mean","AMIN","Median"),each=12)
)

ggplot(mock, aes(Year,Flow, group = factor(Stat), colour = factor(Stat))) +
   coord_cartesian(ylim = c(0, 100)) +
   geom_line(size=1) +
   scale_color_manual(name = "Stat", values = cb8[4:5]) +
   scale_y_continuous(breaks=c(0, 25, 50, 75, 100), labels=c(0, 25, 50, 
75, 100)) +
   facet_wrap(~ fct_relevel(Metric,"AMAX","Mean","AMIN","Median"), nrow 
= 2, ncol = 2) +
   ylab("Flow")


Hope this helps,

Rui Barradas