How to add text in title in ggplot based on value provided by tidy data.frame

Question

I have the following data frame:

df <- structure(list(some_score = c(0.159908755191963, 0.191316882518594, 0.505115802144402, 
  0.137543374720433, 0.00611518542460786, 0.17817657028984, 0.184484678282946, 
  0.389765901467282, 0.240839237211809, 0.00673361274812246), crt = c(0.137543374720433, 
  0.137543374720433, 0.137543374720433, 0.137543374720433, 0.137543374720433, 
  0.17817657028984, 0.17817657028984, 0.17817657028984, 0.17817657028984, 
  0.17817657028984), sr = c(0.374378046673855, 0.374378046673855, 0.374378046673855, 
  0.374378046673855, 0.374378046673855, 0.115542340010558, 0.115542340010558, 
  0.115542340010558, 0.115542340010558, 0.115542340010558), sample = structure(c(1L, 
  1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L), .Label = c("Sample1", "Sample2"), class = "factor"), 
  celltype = c("B", "Mac", "NK", "Neu", "Stro", "B", "Mac", "NK", "Neu", "Stro")), 
  .Names = c("some_score", "crt", "sr", "sample", "celltype"), row.names = c(NA, 
    10L), class = "data.frame")
df
#>     some_score       crt        sr  sample celltype
#> 1  0.159908755 0.1375434 0.3743780 Sample1        B
#> 2  0.191316883 0.1375434 0.3743780 Sample1      Mac
#> 3  0.505115802 0.1375434 0.3743780 Sample1       NK
#> 4  0.137543375 0.1375434 0.3743780 Sample1      Neu
#> 5  0.006115185 0.1375434 0.3743780 Sample1     Stro
#> 6  0.178176570 0.1781766 0.1155423 Sample2        B
#> 7  0.184484678 0.1781766 0.1155423 Sample2      Mac
#> 8  0.389765901 0.1781766 0.1155423 Sample2       NK
#> 9  0.240839237 0.1781766 0.1155423 Sample2      Neu
#> 10 0.006733613 0.1781766 0.1155423 Sample2     Stro

This is the plotting code:

tableau10 <- c("#17BECF", "#BCBD22", "#7F7F7F", "#CFECF9", "#8C564B", "#9467BD", "#D62728", "#2CA02C", "#FF7F0E", "#1F77B4" )
ggplot(df, aes(x=celltype,y=some_score, fill=celltype)) + 
  geom_bar(stat="identity") + 
  scale_fill_manual(values=tableau10) + 
  geom_hline(aes(yintercept=crt), colour="red", linetype="dashed") +
  theme_minimal(base_size=20) +
  theme(strip.background=element_blank(),strip.text = element_text(size=10)) +
  theme(legend.title=element_blank()) +
  theme(axis.text.y=element_text( hjust=1,size=10)) +
  facet_wrap(~sample) 

Which produce this plot:

As shown in the plot that I want to use ggtitle that incorporate values in sr and crt column in the df. How can I do that?

Answer 1

You can try:

# function to round the values. As they are characters you have to use a string manipulation
round_string <- function(string) substr(string, 1, 5)

# the plot
ggplot(df, aes(x=celltype,y=some_score, fill=celltype)) + 
  geom_bar(stat="identity") + 
  scale_fill_manual(values=tableau10) + 
  geom_hline(aes(yintercept=crt), colour="red", linetype="dashed") +
  theme_minimal(base_size=20) +
  theme(strip.background=element_blank(),strip.text = element_text(size=10)) +
  theme(legend.title=element_blank()) +
  theme(axis.text.y=element_text( hjust=1,size=10)) +
  facet_wrap(~sample + crt + sr,labeller = labeller(crt=as_labeller(round_string, default = label_both),
                                                    sr=as_labeller(round_string, default = label_both), 
                                                    .multi_line = F))

Answer 2

Very Basic solution. You can add CRT yourself (sorry did not get so much time now)...

ggplot(df, aes(x=celltype,y=some_score, fill=celltype)) + 
  geom_bar(stat="identity") + 
  scale_fill_manual(values=tableau10) + 
  geom_hline(aes(yintercept=crt), colour="red", linetype="dashed") +
  theme_minimal(base_size=20) +
  theme(strip.background=element_blank(),strip.text = element_text(size=10)) +
  theme(legend.title=element_blank()) +
  theme(axis.text.y=element_text( hjust=1,size=10)) +
  facet_wrap(~paste(as.character(sample), paste("SR = ",round(df$sr,2) )))

With the idea of @Jimbou (labeller) the outcome is really nice too

facet_wrap(~sample+crt+sr, 
  labeller = labeller(crt=label_both, sr = label_both, .multi_line = F))

and you get