RStudio Shiny Error - number of items to replace is not a multiple of replacement length

Question

I am fairly new to R and currently working on a Shiny web app using RStuido to recognise handwritten digits.

The data I am using is from a Kaggle competition: Digit-Recogniser

I have the following function to render average representations of digits

 # Produce a plot containing the average representations of digits

  output$digitAvgRep <- renderImage({

    ## For visualising traing data
    dataFrame<-as.matrix(data())

    ##Color ramp def.
    colors<-c('white','red')
    cus_col<-colorRampPalette(colors=colors)

    ## Plot the average image of each digit
    par(mfrow=c(4,3),pty='s',mar=c(1,1,1,1),xaxt='n',yaxt='n')
    all_img<-array(dim=c(10,28*28))
    for(di in 0:9)
    {
      print(di)
      all_img[di+1,]<-apply(dataFrame[dataFrame[,1]==di,-1],2,sum)
      all_img[di+1,]<-all_img[di+1,]/max(all_img[di+1,])*255

      z<-array(all_img[di+1,],dim=c(28,28))
      z<-z[,28:1] ##right side up1
      image(1:28,1:28,z,main=di,col=cus_col(256))
    }
  })

and I pass the above variable to ui.R using:

# User renderUI to dynamically create objects in the ui.R 
  output$tb <- renderUI({
    if(is.null(data()))
      h5("No data loaded.")
    else
      tabsetPanel(
        tabPanel("About file", tableOutput("filedf")),
        tabPanel("RawData", tableOutput("table")),
        tabPanel("Summary", tableOutput("sum")),
        tabPanel("Digit Distribution",plotOutput("digitDist")),
        tabPanel("Average Digit Representation", imageOutput("digitAvgRep")))
  })

I get the following output when I run the app:

[1] 0
Error in all_img[di + 1, ] <- apply(dataFrame[dataFrame[, 1] == di, -1],  : 
  number of items to replace is not a multiple of replacement length

Anyone know how to solve this?

Thanks

score 0 · Accepted Answer · answered Feb 15 '15 at 22:44

As the error suggest, you are trying to insert a new vector of length that is shorter than the column that you are placed and the number of items is not a multiple of replacement length

using the following as an example :

## create a matrix that is 6 rows and 2 columns
mat <- matrix(1:12, 6,2) 

## try to replace first column with a vector of length 3
## works fine because 6 is a multiple of 3

mat[,1] <- 1:3 

## try to replace first column with a vector of length 5
## Fails because 6 is not a multiple of 5, try the same exception.

mat[,1] <- 1:5 

##   number of items to replace is not a multiple of replacement length

Hence, you may want to reconsider your apply statement. I will consider creating list to store the results instead of trying to store it in a matrix.

Thank you for your response. I had to remove the first column from the input data because the 'all_img' array item size was 28*28=785 and the input data had 786 columns (including the X identifier). Once I removed the identifier column it started working. — umutesen, Feb 16 '15 at 07:58

RStudio Shiny Error - number of items to replace is not a multiple of replacement length

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