davemcg

library(shiny)
library(tidyverse)

genes <- c('A','B','C')
expression <- cbind(rbind(10,100,50),genes) %>% data.frame()
colnames(expression) <- c('Expression','Gene')

shinyServer(function(input, output, session) {
  updateSelectizeInput(session, 'Gene', choices = genes, selected=c('A','C'), server = TRUE)