odd number of plots per page with marrangeGrob

Question

I have a list of plots and am using marrangeGrob to write multiple plots per page. This gives me 6 plots per page:

marrangeGrob(plots, nrow=3, ncol=2, top=NULL)

But what I need is 5 plots per page (i.e. bottom right plot area is left blank)

Here is a reproducible example based on a subset of my data:

> CohData
     Name ScenID ScenName Year VarName Units value
1  Site01      0     Hind 2000     ANC ueq/L 28.23
2  Site02      0     Hind 2000     ANC ueq/L 35.34
3  Site03      0     Hind 2000     ANC ueq/L 31.73
4  Site04      0     Hind 2000     ANC ueq/L 54.21
5  Site05      0     Hind 2000     ANC ueq/L 28.23
6  Site01      1       BC 2020     ANC ueq/L 45.01
7  Site02      1       BC 2020     ANC ueq/L 32.86
8  Site03      1       BC 2020     ANC ueq/L 30.38
9  Site04      1       BC 2020     ANC ueq/L 53.01
10 Site05      1       BC 2020     ANC ueq/L 31.11
11 Site01      0     Hind 2000      pH        6.40
12 Site02      0     Hind 2000      pH        5.93
13 Site03      0     Hind 2000      pH        6.36
14 Site04      0     Hind 2000      pH        5.75
15 Site05      0     Hind 2000      pH        5.16
16 Site01      1       BC 2020      pH        6.63
17 Site02      1       BC 2020      pH        5.86
18 Site03      1       BC 2020      pH        6.33
19 Site04      1       BC 2020      pH        5.73
20 Site05      1       BC 2020      pH        5.23

library(ggplot2)
library(grid)
library(gridExtra)

## Iterate plots and write to PDF
pdf("plots.pdf")
plots <- list()
CohData_nohind <- subset(CohData, ScenID > 0)
stream_vars <- list("ANC", "pH")
for (i in unique(CohData_nohind$ScenID)){
  subdata1 <- subset(CohData_nohind, ScenID == i)
  ScenName <- unique(subdata1$ScenName)
  subdata1 <- subset(CohData, ScenID == i | ScenID == 0)
  for (j in stream_vars){
    subdata2 <- subset(subdata1, VarName == j)
    units <- unique(subdata2$Units)
    for (k in unique(subdata2$Name)){
      subdata3 <- subset(subdata2, Name == k)

      if (j=='ANC'){
        p <- ggplot(subdata3, aes(x = Year, y = value)) + geom_line() + expand_limits(y=c(0,100)) + 
          ggtitle(paste0(as.character(ScenName),":\n", as.character(k))) + ylab(paste0(j, " (", units, ")"))
        plots[[paste(i,j,k,sep="_")]] = p

      } else if (j=='pH'){
        p <- ggplot(subdata3, aes(x = Year, y = value)) + geom_line() + expand_limits(y=c(3,7)) +
          ggtitle(paste0(as.character(ScenName),":\n", as.character(k))) + ylab(paste0(j, " (", units, ")"))
        plots[[paste(i,j,k,sep="_")]] = p
      }
    }
  }
}
interleave <- function(x, y, after = 1){

  nx <- length(x)
  ny <- length(y)

  if((nx %% after) > 0) x <- rep(x, length.out=after * ceiling(nx / after))
  mx <- matrix(x, ncol = after, byrow=TRUE)
  my <- rep(y, length.out = nrow(mx))

  c(t(cbind(mx, my)))
}

x <- replicate(7, ggplot(), simplify=FALSE)
y <- replicate(3, nullGrob(), simplify=FALSE)

marrangeGrob(interleave(x,y,3), ncol=2, nrow=2)
dev.off()

How can I adjust this code for writing each of the 5 "Names" to a single page for each "VarName"?

Answer 1

This version is slightly more general

interleave <- function(x, y, after = 1){

  nx <- length(x)
  ny <- length(y)

  if((nx %% after) > 0) x <- rep(x, length.out=after * ceiling(nx / after))
  mx <- matrix(x, ncol = after, byrow=TRUE)
  my <- rep(y, length.out = nrow(mx))

  c(t(cbind(mx, my)))
}

library(ggplot2)
library(grid)
library(gridExtra)
x <- replicate(7, ggplot(), simplify=FALSE)
y <- replicate(3, nullGrob(), simplify=FALSE)

marrangeGrob(interleave(x,y,3), ncol=2, nrow=2)

Answer 2

I've added the option to pass a layout, let me know if it breaks,

# devtools::install_github("baptiste/gridextra")
library(gridExtra)
library(grid)

gl <- lapply(seq_len(7), function(ii) grobTree(rectGrob(gp=gpar(fill=ii)), 
                                               textGrob(ii)))
marrangeGrob(gl, layout_matrix=matrix(c(1,2,3,NA), 2))

Answer 3

Insert a blank grob in the 6th and 12th positions:

plots[7:11] <- plots[6:10]
plots[[6]] <- textGrob("")
plots[[12]] <- textGrob("")

 pdf("plots.pdf")
 marrangeGrob(plots, nrow=3, ncol=2, top=NULL)
 dev.off()