I am working with a data.table in R where multiple fields can contain multiple values separated by semicolons. I am trying to separate these values into individual rows, with each value corresponding to a new row in the table. However, the challenge is that the separate fields are related and need to be split and expanded correspondingly.

example data:

library(data.table)
df <- data.table(probe = c('A', 'B', 'C'), # there are many columns in real data
                 gene = c('geneA', 'geneB;geneC', 'geneD;geneH;geneI;geneO'), 
                 type = c('mRNA', 'mRNA;miRNA', 'mRNA;miRNA;mRNA;miRNA')
                 ) 

df
    probe                    gene                  type
1:      A                   geneA                  mRNA
2:      B             geneB;geneC            mRNA;miRNA
3:      C geneD;geneH;geneI;geneO mRNA;miRNA;mRNA;miRNA

expected output:

df.new <- data.table(probe = c('A', 'B', 'B', 'C', 'C', 'C', 'C'), 
                     gene = c('geneA', 'geneB', 'geneC', 'geneD', 'geneH', 'geneI', 'geneO'), 
                     type = c('mRNA', 'mRNA', 'miRNA', 'mRNA', 'miRNA', 'mRNA', 'miRNA')
                 )

df.new
    probe   gene   type
1:      A  geneA   mRNA
2:      B  geneB   mRNA
3:      B  geneC  miRNA
4:      C  geneD   mRNA
5:      C  geneH  miRNA
6:      C  geneI   mRNA
7:      C  geneO  miRNA

Thank you for your kindly suggestions