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app.R
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app.R
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#' Jug Application for exposing model as an API
#'
#' @author Alistair Rogers
#'
#' ======= IMPORTING LIBRARIES ===========================================
#'
suppressMessages(library(jsonlite, quietly = T))
suppressMessages(library(dplyr, quietly = T))
suppressMessages(library(jug, quietly = T))
#' ======= LOADING SERIALISED MODEL AND PREPROCESSING ====================
#'
model <- readRDS('model.RDS')
preprocessing <- readRDS('preprocessing.RDS')
#' ============= PREDICTION METHOD =======================================
#' @param json: JSON string of Sepal.Length, Sepal.Width, Petal.Length,
#' Petal.Width
#' @concepts Read in JSON string of predictors (described above) and apply
#' preprocessing and predict Species.
#' @return result: JSONised dataframe of predictor columns with their species prediction
prediction <- function(json) {
if (validate(json)){
df <- fromJSON(json) %>%
as.data.frame()
result <- df %>%
predict(preprocessing, newdata = .) %>% # Apply Preprocessing - Centering and Scaling
predict(model, newdata = .) %>% # Apply XGBoost Model
data.frame(Species = .) %>% # Turn predictions into Dataframe
cbind(df, .) %>% # Concatenate
toJSON(pretty = T)
} else {
result <- list(error = 400, message = 'Not Valid JSON')
}
return(result)
}
#' ========== TEST METHOD ==============================================
test_func <- function() {
message <- 'Why Hello there chap'
message %>% toJSON()
}
#' ========== MAIN METHOD - API ENDPOINT ===============================
main <- function() {
jug() %>%
post("/prediction", decorate(prediction)) %>% # Prediction Method
get("/", decorate(test_func)) %>% # Test Method
simple_error_handler_json() %>%
serve_it(host = '0.0.0.0', port = 8080) # Docker container will not work unless it's on this host.
}
main()