Is there a simple way to do this in R:
plot(var1,var2, for all observations in the data frame where var3 < 155)
It is possible by creat
with(dfr[dfr$var3 < 155,], plot(var1, var2)) should do the trick.
with(dfr[dfr$var3 < 155,], plot(var1, var2))
Edit regarding multiple conditions:
with(dfr[(dfr$var3 < 155) & (dfr$var4 > 27),], plot(var1, var2))