Question

I know the title makes this sound very easy, but I have a For loop that graphs my data. As the values vary, so too does the limits of the X-axis (different start and end for each plot). However, I want to have a defined X-axis range that stays the same for all similar plots. This is complicated by the fact that there are ~40 possible ranges for the X that I want.

I have a data frame of the x-lims I would like to choose from, for each plot. It basically looks like:

   Trait  start    end
    A     123456   134567
    B     234546   245678
    C     234546   245678
    D     345678   356789

and so on. So, if one loop gives me the values: Trait C, start = 235000 and end = 240000, I would like to automatically use the third set of default X-lims.

edit: added more info (Trait).

Answer 1

If your displayed data.frame is called df (and your are sure your variable end will be greater than start), this should work:

which(start > df$start & end < df$end)[1]

---

Revised to answer revised question

As you add more conditions, you can extend the logic above:

## Make your data easily reproducible for others
df <- read.table(text="Trait  start    end
    A     123456   134567
    B     234546   245678
    C     234546   245678
    D     345678   356789", header=TRUE)

## Set values from within your example loop
Trait <- "C"
start <- 235000
end <- 240000

## Get index of desired row
i <- which(Trait==df$Trait & start > df$start & end < df$end)[1]
## Extract xlim values in the form of a numeric vector
myxlim <- unname(unlist(df[i, c("start", "end")]))
myxlim
[1] 234546 245678