Adding a row into a new element based on the name of another column

I am trying to place the three groups in PlantGrowth into 3 separate datasets to make 3 boxplots (using base r, but I am fine using ggplots as well). Currently my idea is to use an if function, but as I'm not too used to R it isn't working out how I want it to.

Currently I'm working on something along the lines of this to place them separately. Is there an easier way to do this? Or maybe a way to make the if function work?

You dont need to separate into three different datasets to get three box plots. If you want them in all three in separate, individual plots, you can use sapply (or a for loop), which will iterate through the different levels and output a separate box plot for each group:

sapply(unique(PlantGrowth$group), 
       function(x) boxplot(PlantGrowth[PlantGrowth$group %in% x, "weight"], 
                           main = x))

# or 
for(plnt in unique(PlantGrowth$group)){
  x <- PlantGrowth[PlantGrowth$group %in% plnt, ]
  boxplot(x$weight, main = plnt)
}

This will output three individual plots like below (using trt2 as an example since it was the last output, but similar for the other two groups):

If you want them all faceted in one visual, you can use par and mfrow:

par(mfrow = c(2,2))
sapply(unique(PlantGrowth$group), 
       function(x) boxplot(PlantGrowth[PlantGrowth$group %in% x, "weight"], 
                           main = x))

For completeness, of course if you want them all on the same plot you can simply do:

boxplot(PlantGrowth$weight ~ PlantGrowth$group)