Conditionally plot multiple variables (grouped data) in loop in R

Question

I have seen several conditional plotting as well as grouped data questions (e.g. here and here) but my problem is different. I have following sample data dat in my R dataframe. The data contains five columns, i.e., Grp (character), Var (integer) (unequal rows for each group), Col1 (numeric), Col2 (numeric), Col3 (numeric).

Grp     Var    Col1  Col2    Col3
grp_1   8      46.8  50.0   50.6
grp_1   16     95.6  47.4   48.0
grp_1   24     45.1  45.6   46.4
grp_1   32     68.8  44.3   58.2
grp_1   40     44.6  52.2   44.3
grp_1   48     86.5  42.2   68.6
grp_2   40     63.2  95.6   63.0
grp_2   60     66.7  67.5   65.6
grp_2   80     69.6  70.7   67.9
grp_2   100    71.9  73.4   69.3
grp_2   120    73.8  75.7   48.0
grp_3   500    51.9  50.0   50.5
grp_3   1000   65.5  53.0   53.4
grp_3   5000   61.2  99.0   59.9
grp_3   10000  80.1  63.0   62.8
grp_3   30000  25.9  33.8   14.2

For each group, I would like to plot columns Col1, Col2, Col3 (y-axis) against Var (x-axis), and conditionally change x-axis title as "steps", "number1", and "number2" for Var values corresponding to grp_1, grp_2 and grp_3. I see a relevant question on conditionally changing labels for two variables here but couldn't find for three variables. I need to plot above data for several groups (both in individual plots written to local disk and grid of 4 plots) so I am looking for suggestions on loop and/or function approaches. Can somebody suggest on how this could be achieved?

Using your links, please make an attempt and *show* (not tell) your desired output. — Parfait, Apr 21 '20 at 13:41
I am not sure I understand correctly. Your x-axis is numeric but you want to modify the axis ticks labels to show "step 1", "step 2" etc instead of 8, 16 etc? — desval, Apr 21 '20 at 14:06
My bad, I meant axis titles. I meant, for each group, if `Var` values are `c(8,16.24,32,40,48)` then x-axis title needs to be "steps", if `c(40,60,80,100,120)` then title "number1" and if `c(500,1000,5000,10000,30000)` then "number2". Hope it makes sense now? — khajlk, Apr 21 '20 at 14:15

desval · Answer 1 · 2020-04-21T16:20:55.330

I am still not sure about the desired output, you should maybe show what you have tried so far...

d <- read.table(text = 
  "Grp     Var    Col1  Col2    Col3
grp_1   8      46.8  50.0   50.6
grp_1   16     95.6  47.4   48.0
grp_1   24     45.1  45.6   46.4
grp_1   32     68.8  44.3   58.2
grp_1   40     44.6  52.2   44.3
grp_1   48     86.5  42.2   68.6
grp_2   40     63.2  95.6   63.0
grp_2   60     66.7  67.5   65.6
grp_2   80     69.6  70.7   67.9
grp_2   100    71.9  73.4   69.3
grp_2   120    73.8  75.7   48.0
grp_3   500    51.9  50.0   50.5
grp_3   1000   65.5  53.0   53.4
grp_3   5000   61.2  99.0   59.9
grp_3   10000  80.1  63.0   62.8
grp_3   30000  25.9  33.8   14.2
  ", header=T
)

library(ggplot2)
library(data.table)

d <- setDT(d)
dd <- melt(d, id.vars = c("Grp", "Var"), measure.vars = patterns(col="Col") )

ggplot(dd, aes(Var, value, color=variable)) + 
  geom_point() +
  facet_wrap(~Grp,
             scales = "free",
             labeller = as_labeller(c(grp_1 = "Step 1", grp_2 = "Step 2", grp_3 = "Step 3")  ),
             strip.position = "bottom") +
  xlab(NULL) +
  theme(strip.background = element_blank(),
        strip.placement = "outside")

I noticed in your answer, you used `c(grp_1="Step1"....)` to name the x-axis. I needed condition here, maybe `ifelse`, to check if x-axis values are e.g. `c(8,16,24,32,40,48)` then label needs to be "Steps" and so on.., please see my updated explanation in the comment above. — khajlk, Apr 21 '20 at 15:58
You will probably make your life a lot simpler if you check the condition before you plot the data, since the x-axis values are determined by your facet variable. In the data you provided, each group has different x-axis variables. — desval, Apr 21 '20 at 16:14

Conditionally plot multiple variables (grouped data) in loop in R

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