Image classification error in Rstudio for keras

[joelt92]

I tried to run the code below for image classification using keras. My motive is to detect if the image is a dog or cat.

> library(keras)
> image_path = 'C:/Users/Joel/Desktop/SJU/Semester 3/R programming/Cat_photo.jpg'
> 
> # define image preprocessor for use with keras vgg19
> image_preprocessor = function(image_path) {
>   image = image_load(image_path, target_size = c(224,224))
>   image = image_to_array(image)
>   image = array_reshape(image, c(1, dim(image)))
>   image = imagenet_preprocess_input(image)
>   return(image)
> }
> 
> #function to read in files housing all cat/dog breeds in imagenet labels
> read_dog_cat_labels = function(path) {
>   labs = readLines(path)
>   labs = trimws(unlist(strsplit(labs, ',')))
>   labs = gsub('\\s+', '_', labs)
>   return(labs)
> }
> 
> #doubt 22 to 26
> # define image paths to classify
> image_paths = list.files('images', recursive = TRUE, full.names = TRUE)
> 
> # preprocess images
> image_list = lapply(image_paths, image_preprocessor)
> 
> # load vgg19 model pretrained with imagenet
> model = application_vgg19(weights = 'imagenet')
> 
> # get model prediction
> preds = lapply(image_list, function(i) {
>   imagenet_decode_predictions(predict(model, i), top = 1)[[1]]
> })
> 
> 
> # convert list of predictions to df and drop class name column
> pred_df = do.call(rbind, preds)
> pred_df$class_name = NULL
> 
> #read in breed labels
> dog_labs = read_dog_cat_labels('C:/Users/Joel/Desktop/SJU/Semester 3/R programming/dog_classes.txt')
> cat_labs = read_dog_cat_labels('C:/Users/Joel/Desktop/SJU/Semester 3/R programming/cat_classes.txt')
> 
> #create column for labeling dog breeds as dog and cat breeds as cat
> pred_df$catdog = NA
> pred_df$catdog[pred_df$class_description %in% dog_labs] = 'Dog'
> pred_df$catdog[pred_df$class_description %in% cat_labs] = 'Cat'
> 
> #add column with image paths
> pred_df$file_name = unlist(image_paths)
> pred_df = pred_df[order(pred_df$score),]
> print(pred_df)
>

However, I get the below error:

> pred_df = pred_df[order(pred_df$score),]
Error in order(pred_df$score) : argument 1 is not a vector
> print(pred_df)
$catdog
[1] NA

$file_name
character(0)

How can I resolve this?

[ablack3]

How about checking that pred_df$score is a vector? Try looking at the output of str(pred_df$score).

[joelt92]

I checked, I also attempted order(1-pred_df$score) but no luck

[jcblum]

It's difficult to figure out what's happening here because we can't run your code (it depends on files in your local file system). When asking questions about code problems, it's good to try to create a reproducible example, if at all possible. See: FAQ: Tips for writing R-related questions.

That said, the error is coming from order(), which of course doesn't itself have anything to do with the image classification part . The order() code looks OK on its face, so that suggests that pred_df has perhaps not actually been created with the structure you're expecting. Can you please paste in the output of running str(pred_df)?