I have a problem with "Error in comp[[i]] : subscript out of bounds"

I want to indicate compact letter display in my analysis but it did not work.

I have tried to find some solution in internet but it failed.

Do anyone can help me?

this is my data data

and this is the script

```
library(datasets)
library(ggplot2)
library(multcompView)
library(dplyr)
library(datasets)
library(tidyverse)
library(multcomp)
Data = read.csv("data.csv", h= TRUE)
qplot(x = species, y = Ratio, geom = "point", data = Data) +
facet_grid(.~Strain)
# creating a variable as factor for the ANOVA
Data$Strain <- as.factor(Data$Strain)
Data$species <- as.factor(Data$species)
str(Data)
# analysis of variance
anova <- aov(Ratio ~ Strain*factor(species), data = Data)
summary(anova)
# table with factors, means and standard deviation
data_summary <- group_by(Data, Strain, species) %>%
summarise(mean=mean(Ratio), sd=sd(Ratio)) %>%
arrange(desc(mean))
print(data_summary)
# Tukey's test
tukey <- TukeyHSD(anova)
print(tukey)
# compact letter display
coba = multcompLetters4(anova, tukey)
print(coba)
# creating the compact letter display
tukey.cld <- multcompLetters4(anova, tukey)
print(tukey.cld)
```

this is what I want to get ---> I want to get the letter indicate in my data

Please help me!

Thank you so much