create_diag

create_diag <- function(data, expr, colvec, ignore.case = T){
  #regexp=regular expressions for the data
  # colvec = vector of the columns of interest (columns with the diagnoses)
  require(dplyr, quietly = T)
  require(tidyr, quietly = T)
  # select the variables of interest
  sel <- names(data)[colvec]
  # ensure they are all the variables are character vectors and create a data subset of the variables
  df <- as_data_frame(data[sel]) %>% mutate_each(funs(as.character))
  # a function to assign "1" if the regular expression matched or "0" otherwise 
  f <- function(x) grepl(expr, x, ignore.case = ignore.case)+0
  # apply the function above to all the cells in the data frame "df"
  df <- sapply(df, f) 
  df <- as_data_frame(df)  %>% mutate(new_diag = rowSums(., na.rm = TRUE)) %>% select(new_diag)
  # the vector of the new variable (new diagnosis) to add to the data frame (data)
  as.factor(as.numeric((df[,1] > 0))) 
  
}