Boxplots are regular in data analysis. Some times you may want to highlight points. In biology, let us you have box plot for Tumor and Normal samples and then you want to highlight certain gene. Let us assume that expression data is in a data frame and you want to draw a box plot and then highlight certain gene with different colors. Following is the code: In the following code, we simulate gene expression data (as data frame and highlight one of them)

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## Create a data frame for two samples:Normal and Tumor

df=data.frame(normal=rnorm(10,60,5), tumor=rnorm(10,70,4))

## Add row names with gene_1, gene_2, gene_3..so on

row.names(df)=paste0("gene_",seq(1:10))

## Draw box plot

boxplot(df)

## Highlight gene_4 and color by colnames

stripchart(df["gene_4",], vertical = T, method = "jitter", add=T, pch=20, col=as.factor(colnames(df)))

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output looks as follows:

Gene_4 is highlighted by black dot in normal and by red, in tumor