Manipulating textInput in R Shiny - r

Question

I am relatively new to R and even more new to Shiny (literally first day).
I would like a user to input multiple phrases separated by a comma such as female, aged, diabetes mellitus. I have a dataframe in which one variable, MH2 contains text words. I would like to output a dataframe that contains only the rows in which all of the inputted phrases are present. Sometimes a user may input only one phrase, other times 5.
This is my ui.R
library(shiny)
library(stringr)
# load dataset
load(file = "./data/all_cardiovascular_case_reports.Rdata")
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
textInput(inputId = "phrases",
label = "Please enter all the MeSH terms that you would like to search, each separated by a comma:",
value = ""),
helpText("Example: female, aged, diabetes mellitus")
),
mainPanel(DT::dataTableOutput("dataframe"))
)
)
and here is my server.R
library(shiny)
server <- function(input, output)
{
# where all the code will go
df <- reactive({
# counts how many phrases there are
num_phrases <- str_count(input$phrases, pattern = ", ") + 1
a <- numeric(num_phrases) # initialize vector to hold all phrases
# create vector of all entered phrases
for (i in 1:num_phrases)
{
a[i] <- noquote(strsplit(input$phrases, ", ")[[i]][1])
}
# make all phrases lowercase
a <- tolower(a)
# do exact case match so that each phrase is bound by "\\b"
a <- paste0("\\b", a, sep = "")
exact <- "\\b"
a <- paste0(a, exact, sep = "")
# subset dataframe over and over again until all phrases used
for (i in 1:num_phrases)
{
final <- final[grepl(pattern = a, x = final$MH2, ignore.case = TRUE), ]
}
return(final)
})
output$dataframe <- DT::renderDataTable({df()})
}
When I tried running renderText({num_phrases}) I consistently got 1 even when I would input multiple phrases separated by commas. Since then, whenever I try to input multiple phrases, I run into "error: subscript out of bounds." However, when I enter the words separated by a comma only versus a comma and space (entering "female,aged" instead of "female, aged") then that problem disappears, but my dataframe doesn't subset correctly. It can only subset one phrase.
Please advise.
Thanks.

Answer 1

I think your Shiny logic looks good, but the function for subsetting the dataframe has a few small issues. In particular:
a[i] <- noquote(strsplit(input$phrases, ", ")[[i]][1])
The indices [[i]] and 1 are in the wrong place here, should be [[1]][i]
final <- final[grepl(pattern = a, x = final$MH2, ignore.case = TRUE), ]
You can not match multiple patterns like this, only the first element of a will be used, which is also the warning R gives.
Example working code
I have changed input$phrases to inp_phrases here. If this script does what you want I think you can easily copy it into you reactive, making the necessary changes (i.e. changing inp_phrases back, and adding the return(result) statement.). I was also not entirely clear if you wanted all patterns to be matched within one row, or return all rows were any of the patterns were matched, so I added them both, you can uncomment the one you need:
library(stringr)
# some example data
inp_phrases = "ab, cd"
final = data.frame(index = c(1,2,3,4),MH2 = c("ab cd ef","ab ef","cd ef ab","ef gx"),stringsAsFactors = F)
# this could become just two lines:
a <- sapply(strsplit(inp_phrases, ", ")[[1]], function(x) tolower(noquote(x)))
a <- paste0("\\b", a, "\\b")
# Two options here, uncomment the one you need.
# Top one: match any pattern in a. Bottom: match all patterns in a
# indices = grepl(pattern = paste(a,collapse="|"), x = final$MH2, ignore.case = TRUE)
indices = colSums(do.call(rbind,lapply(a, function(x) grepl(pattern = x, x = final$MH2, ignore.case = TRUE))))==length(a)
result <- final[indices,]
Returns:
index MH2
1 1 ab cd ef
3 3 cd ef ab
... with the second version of indices (match all) or
index MH2
1 1 ab cd ef
2 2 ab ef
3 3 cd ef ab
... with the first version of indices (match any)
Hope this helps!