问题
I'm trying to develop a simple app that fetches local classified ads from Kijiji website. I have made a similar app with pretty much the same exact script but I'm not getting the error described below so I don't know what has gone wrong with this script. I tried everything I could think of, but couldn't get it to work.
the structure of the df dataframe in server.R is as follows: (note that I have truncated the values to make it more readable)
'data.frame': 38 obs. of 7 variables:
$ Title : chr "Baby-boy 3-6 month" ...
$ Price : num 0 6.92 8 10 10 15 15 15 20 20 ...
$ Short.Description: chr "Give for free ..."
$ Address : chr "Calgary, AB T2Z 0V6" "341 ..."
$ Date : Date, format: "2014-12-05" "2014-10-28" "2014-12-05" ...
$ Full.Description : chr "Give for free some ..."
$ Link : chr "http://www.kijiji...."
and can be replicated as follows:(a sample with 5 records for demonstration purposes)
df <- data.frame(
Title= c("Baby-boy 3-6 month","Giggle Life Optimize Cloth Diapers & 4 layer mixed insert", "Beluga Baby","Baby sled", "Avent Sterilizer & Various Medela Items"),
Price= c(0.00, 6.92, 8.00, 10.00, 10.00),
Short.Description=c("Give for free some staff for boy 3-6 month. Live in New Brighton, SE", "If you have any questions or are looking to order please don't hesitate to call our local line 587-774-2404, toll free line 1-877-883-3069 or visit our website…","Calgary! Fall in love with your all natural and freshly handmade products for mama and baby. www.belugaskincare.com Like us on Facebook.com/belugaskincare FREE shipping in Canada with a $25 cart!…", "Yellow plastic baby sled Safety seat belt Tow rope Dimensions: 23\" long x 14 1/2\" wide x 12\" high $10 Located in Willow Park off Southland Dr. and Fairmount Dr. SE CALL: 403 460 - 0978 (will not…", "Avent microwave sterilizer in good condition 1 Avent bottle 2 Medela bottles 1/2 box of unused Medela pump and save bags 1bag of replaceable Medela pump parts From clean, smoke free home. Take all…"),
Address=c("Calgary, AB T2Z 0V6","341 Westvale Drive, Waterloo, ON N2T 2M2","Canada", "Calgary, AB T2J 1H6, Canada","Calgary, AB T2W, Canada"),
Date=c(as.Date(c( "2014-12-05", "2014-10-28", "2014-12-05", "2014-12-05", "2014-12-05"))),
Full.Description=c("Give for free some staff for boy 3-6 month. Live in New Brighton, SE", "If you have any questions or are looking to order please don't hesitate to call our local line 587-774-2404, toll free line 1-877-883-3069 or visit our website http://www.gigglelife.com/catalog/?Calgary. \rEnter the promo code \"KIJCALGARY\" in the comment box when ordering to receive a free gift with your order.\rThe new Giggle Life Optimize Cloth Diaper is very affordable, effective, and comfortable. It is simply the best value on market. These reusable diapers are one size fits all (7-36lbs). \rThey are $6.92 each when you purchase 12. Please note there is a $1 surcharge for pattern designs. \rManufacturer’s Warranty \rSupport for as long as you use the diapers! \r****FREE SHIPPING ACROSS CANADA!!**** \rAll diapers are new and individually packaged - never worn OR washed. They are high quality, one-size-fits-all, pocket cloth diapers. \rAll orders are shipped via Canada Post within 24 hours of placing your order. We send all packages Expedited with insurance and a tracking number, which is provided immediately upon shipping out. \rLooking for other package sizes? We have packages of 10, 24, 38 and 100 also..", "Calgary! Fall in love with your all natural and freshly handmade products for mama and baby. www.belugaskincare.com Like us on Facebook.com/belugaskincare FREE shipping in Canada with a $25 cart! \"making life simpler and greener so you can better do the things you are most passionate about\" - Beluga Skin CareThis ad was posted with the Kijiji mobile app.This ad was posted WITH the Kijiji mobile app.", "Yellow plastic baby sledSafety seat beltTow ropeDimensions: 23\" long x 14 1/2\" wide x 12\" high$10Located in Willow Park off Southland Dr. and Fairmount Dr. SECALL: 403 460 - 0978 (will not respond to texts at this land line number) TEXT OR CALL: 403 463 - 1038PLEASE SEE MY OTHER ADSThis ad was posted with the Kijiji mobile app.This ad was posted WITH the Kijiji mobile app.","Avent microwave sterilizer in good condition1 Avent bottle2 Medela bottles1/2 box of unused Medela pump and save bags1bag of replaceable Medela pump partsFrom clean, smoke free home. Take all for 10$This ad was posted with the Kijiji mobile app.This ad was posted WITH the Kijiji mobile app."),
Link= c("http://www.kijiji.ca/v-baby-clothes-3-6-months/calgary/baby-boy-3-6-month/1037502424","http://www.kijiji.ca/v-baby-bathing-changing-diapers/calgary/giggle-life-optimize-cloth-diapers-4-layer-mixed-insert/1008481541?src=topAdSearch", "http://www.kijiji.ca/v-baby-bathing-changing-diapers/calgary/beluga-baby/1037483143" , "http://www.kijiji.ca/v-baby-toy/calgary/baby-sled/1037493662", "http://www.kijiji.ca/v-baby-feeding-high-chair/calgary/avent-sterilizer-various-medela-items/1037481182" )
)
here's server.R. Note that I have commented out the source code to avoid providing the source code and delayed computation. Please use the df dataframe given above to reproduce the results:
#Install required packages
ListofPackages= c('shiny','ggplot2','scales')
NewPackages= ListofPackages[!(ListofPackages %in% installed.packages()[,'Package'])]
if(length(NewPackages)>0) install.packages(NewPackages)
#Load required packages
lapply(ListofPackages,require,character.only=TRUE)
#Load source code
#source('C:/Users/Bahae.Omid/Google Drive/My R Case Studies/Shiny Apps/Kijiji App/adscraper.R',local=TRUE)
shinyServer(function(input,output){
#Create a reactive function to deal with inputs of the user
search <- reactive({
if(length(input$t)>0) {ind <- grep(input$t,df[,'Title'],ignore.case = T); df <- df[ind,] }
if(length(input$d)>0) {ind <- grep(input$d,df[,'Full.Description'],ignore.case = T); df <- df[ind,]}
if(length(input$a)>0) {ind <- grep(input$a,df[,'Address'],ignore.case = T); df <- df[ind,]}
if(input$p >=0) {ind <- df[,'Price']<=input$p ; df <- df[ind,]}
})
#Send the searchresult table to ui.R
output$searchresult <- renderDataTable({
input$action1 #triggered only when button is pressed
if(input$action1==0) return()
else{isolate({
transformed <- transform(search(), URL = paste('<a href = ', shQuote(Link), '>', 'Click</a>'))
transformed[-7] #Remove the old Link column
})
}
}, option=list(autoWidth=FALSE,pageLength=100,
columnDefs = list(list(targets =c(2,5,7) -1, searchable = FALSE),list(sWidth="75px",aTargets = list(4,5)))))
#Allow user to download the data via downloadhandler
output$down <- downloadHandler(
filename='filtered.csv',
content=function(file){write.csv(search(),file,row.names=FALSE)}
)
})
and here's ui.R. Note that I have commented out the image tags to avoid errors when running the code:
shinyUI(fluidPage(
#Display datatable filters on top
tags$head(tags$style("tfoot {display: table-header-group;}")),
#Add a title
#img(src="kijiji.gif", height = 100, width = 100),
#img(src="plus.png", height = 20, width = 20),
#img(src="plus.png", height = 20, width = 20),
#Use the Sidebar layout
sidebarLayout(
sidebarPanel(
#Add fields to search by and download button to allow exporting search results to csv.
h5('Note: Running the app takes a little while to run at startup.'),
helpText('Ad Title:'),
textInput('t',''),
helpText('Description:'),
textInput('d',''),
helpText('Address:'),
textInput('a',''),
sliderInput('p','Show Prices up to:',min = 0,max = 10000,step = 50,value = 10000),
actionButton('action1','Search!'),
br(),
br(),
helpText('Click below to download the results of your search:'),
downloadButton('down','Download')
),
mainPanel(
dataTableOutput('searchresult')
)
)
))
When I run the app, all filters seem to work fine but when a filter returns no records from the data frame (i.e. 0-row dataframe), I get the following error:
Error in data.frame(structure(list(Title = character(0), Price = numeric(0), :
arguments imply differing number of rows: 0, 1
I have tested the same script using renderTable as opposed to renderDataTable and it worked perfectly fine. But I would like the output in DataTable format, specially that I was able to make it work in another identical app.
Please let me know if you need more clarification.
回答1:
When search() returns a data.frame with zero rows
paste('<a href = ', shQuote(search()$url), '>', 'Click</a>')
returns
"<a href = \"\" > Click</a>"
You are then trying to bind this new column with one row to your data.frame with no rows. Hence the error message.
You can fix it using something like
transformed <- transform(search()
, Link = if(length(url) > 0){
paste('<a href = ', shQuote(url), '>', 'Click</a>')
}else{
character(0)
}
)
回答2:
Basically the error says: there is nothing to display. So use browser() and check what is the current output in console
来源：https://stackoverflow.com/questions/27325855/shiny-error-arguments-imply-differing-number-of-rows