Analyzing rtweet Information with kerasformula

Overview

The kerasformula package deal affords a high-level interface for the R interface to Keras. It’s foremost interface is the kms perform, a regression-style interface to keras_model_sequential that makes use of formulation and sparse matrices.

The kerasformula package deal is offered on CRAN, and may be put in with:

# set up the kerasformula package deal
set up.packages("kerasformula")    
# or devtools::install_github("rdrr1990/kerasformula")

library(kerasformula)

# set up the core keras library (if you have not already finished so)
# see ?install_keras() for choices e.g. install_keras(tensorflow = "gpu")
install_keras()

The kms() perform

Many traditional machine studying tutorials assume that knowledge are available in a comparatively homogenous kind (e.g., pixels for digit recognition or phrase counts or ranks) which might make coding considerably cumbersome when knowledge is contained in a heterogenous knowledge body. kms() takes benefit of the flexibleness of R formulation to easy this course of.

kms builds dense neural nets and, after becoming them, returns a single object with predictions, measures of match, and particulars in regards to the perform name. kms accepts plenty of parameters together with the loss and activation capabilities present in keras. kms additionally accepts compiled keras_model_sequential objects permitting for even additional customization. This little demo reveals how kms can help is mannequin constructing and hyperparameter choice (e.g., batch dimension) beginning with uncooked knowledge gathered utilizing library(rtweet).

Let’s have a look at #rstats tweets (excluding retweets) for a six-day interval ending January 24, 2018 at 10:40. This occurs to provide us a pleasant affordable variety of observations to work with when it comes to runtime (and the aim of this doc is to indicate syntax, not construct significantly predictive fashions).

rstats <- search_tweets("#rstats", n = 10000, include_rts = FALSE)
dim(rstats)

  [1] 2840   42

Suppose our aim is to foretell how widespread tweets will probably be based mostly on how usually the tweet was retweeted and favorited (which correlate strongly).

cor(rstats$favorite_count, rstats$retweet_count, methodology="spearman")

    [1] 0.7051952

Since few tweeets go viral, the information are fairly skewed in the direction of zero.

Getting probably the most out of formulation

Let’s suppose we’re all for placing tweets into classes based mostly on reputation however we’re undecided how finely-grained we wish to make distinctions. A few of the knowledge, like rstats$mentions_screen_name is available in an inventory of various lengths, so let’s write a helper perform to rely non-NA entries.

Let’s begin with a dense neural web, the default of kms. We will use base R capabilities to assist clear the information–on this case, lower to discretize the end result, grepl to search for key phrases, and weekdays and format to seize totally different elements of the time the tweet was posted.

breaks <- c(-1, 0, 1, 10, 100, 1000, 10000)
reputation <- kms(lower(retweet_count + favorite_count, breaks) ~ screen_name + 
                  supply + n(hashtags) + n(mentions_screen_name) + 
                  n(urls_url) + nchar(textual content) +
                  grepl('photograph', media_type) +
                  weekdays(created_at) + 
                  format(created_at, '%H'), rstats)
plot(reputation$historical past) 
  + ggtitle(paste("#rstat reputation:", 
            paste0(spherical(100*reputation$evaluations$acc, 1), "%"),
            "out-of-sample accuracy")) 
  + theme_minimal()

reputation$confusion

reputation$confusion

                    (-1,0] (0,1] (1,10] (10,100] (100,1e+03] (1e+03,1e+04]
      (-1,0]            37    12     28        2           0             0
      (0,1]             14    19     72        1           0             0
      (1,10]             6    11    187       30           0             0
      (10,100]           1     3     54       68           0             0
      (100,1e+03]        0     0      4       10           0             0
      (1e+03,1e+04]      0     0      0        1           0             0

The mannequin solely classifies about 55% of the out-of-sample knowledge accurately and that predictive accuracy doesn’t enhance after the primary ten epochs. The confusion matrix means that mannequin does greatest with tweets which are retweeted a handful of occasions however overpredicts the 1-10 stage. The historical past plot additionally means that out-of-sample accuracy isn’t very steady. We will simply change the breakpoints and variety of epochs.

breaks <- c(-1, 0, 1, 25, 50, 75, 100, 500, 1000, 10000)
reputation <- kms(lower(retweet_count + favorite_count, breaks) ~  
                  n(hashtags) + n(mentions_screen_name) + n(urls_url) +
                  nchar(textual content) +
                  screen_name + supply +
                  grepl('photograph', media_type) +
                  weekdays(created_at) + 
                  format(created_at, '%H'), rstats, Nepochs = 10)

plot(reputation$historical past) 
  + ggtitle(paste("#rstat reputation (new breakpoints):",
            paste0(spherical(100*reputation$evaluations$acc, 1), "%"),
            "out-of-sample accuracy")) 
  + theme_minimal()

That helped some (about 5% further predictive accuracy). Suppose we wish to add a bit extra knowledge. Let’s first retailer the enter components.

pop_input <- "lower(retweet_count + favorite_count, breaks) ~  
                          n(hashtags) + n(mentions_screen_name) + n(urls_url) +
                          nchar(textual content) +
                          screen_name + supply +
                          grepl('photograph', media_type) +
                          weekdays(created_at) + 
                          format(created_at, '%H')"

Right here we use paste0 so as to add to the components by looping over consumer IDs including one thing like:

grepl("12233344455556", mentions_user_id)

mentions <- unlist(rstats$mentions_user_id)
mentions <- distinctive(mentions[which(table(mentions) > 5)]) # take away rare
mentions <- mentions[!is.na(mentions)] # drop NA

for(i in mentions)
  pop_input <- paste0(pop_input, " + ", "grepl(", i, ", mentions_user_id)")

reputation <- kms(pop_input, rstats)

That helped a contact however the predictive accuracy remains to be pretty unstable throughout epochs…

Customizing layers with kms()

We might add extra knowledge, maybe add particular person phrases from the textual content or another abstract stat (imply(textual content %in% LETTERS) to see if all caps explains reputation). However let’s alter the neural web.

The enter.components is used to create a sparse mannequin matrix. For instance, rstats$supply (Twitter or Twitter-client utility sort) and rstats$screen_name are character vectors that will probably be dummied out. What number of columns does it have?

    [1] 1277

Say we needed to reshape the layers to transition extra steadily from the enter form to the output.

reputation <- kms(pop_input, rstats,
                  layers = record(
                    items = c(1024, 512, 256, 128, NA),
                    activation = c("relu", "relu", "relu", "relu", "softmax"), 
                    dropout = c(0.5, 0.45, 0.4, 0.35, NA)
                  ))

kms builds a keras_sequential_model(), which is a stack of linear layers. The enter form is decided by the dimensionality of the mannequin matrix (reputation$P) however after that customers are free to find out the variety of layers and so forth. The kms argument layers expects an inventory, the primary entry of which is a vector items with which to name keras::layer_dense(). The primary component the variety of items within the first layer, the second component for the second layer, and so forth (NA as the ultimate component connotes to auto-detect the ultimate variety of items based mostly on the noticed variety of outcomes). activation can also be handed to layer_dense() and should take values resembling softmax, relu, elu, and linear. (kms additionally has a separate parameter to regulate the optimizer; by default kms(... optimizer="rms_prop").) The dropout that follows every dense layer fee prevents overfitting (however in fact isn’t relevant to the ultimate layer).

Selecting a Batch Measurement

By default, kms makes use of batches of 32. Suppose we have been pleased with our mannequin however didn’t have any explicit instinct about what the dimensions ought to be.

Nbatch <- c(16, 32, 64)
Nruns <- 4
accuracy <- matrix(nrow = Nruns, ncol = size(Nbatch))
colnames(accuracy) <- paste0("Nbatch_", Nbatch)

est <- record()
for(i in 1:Nruns){
  for(j in 1:size(Nbatch)){
   est[[i]] <- kms(pop_input, rstats, Nepochs = 2, batch_size = Nbatch[j])
   accuracy[i,j] <- est[[i]][["evaluations"]][["acc"]]
  }
}
  
colMeans(accuracy)

    Nbatch_16 Nbatch_32 Nbatch_64 
    0.5088407 0.3820850 0.5556952 

For the sake of curbing runtime, the variety of epochs was set arbitrarily brief however, from these outcomes, 64 is the most effective batch dimension.

Making predictions for brand new knowledge

To this point, we’ve been utilizing the default settings for kms which first splits knowledge into 80% coaching and 20% testing. Of the 80% coaching, a sure portion is put aside for validation and that’s what produces the epoch-by-epoch graphs of loss and accuracy. The 20% is simply used on the finish to evaluate predictive accuracy.
However suppose you needed to make predictions on a brand new knowledge set…

reputation <- kms(pop_input, rstats[1:1000,])
predictions <- predict(reputation, rstats[1001:2000,])
predictions$accuracy

    [1] 0.579

As a result of the components creates a dummy variable for every display identify and point out, any given set of tweets is all however assured to have totally different columns. predict.kms_fit is an S3 methodology that takes the brand new knowledge and constructs a (sparse) mannequin matrix that preserves the unique construction of the coaching matrix. predict then returns the predictions together with a confusion matrix and accuracy rating.

In case your newdata has the identical noticed ranges of y and columns of x_train (the mannequin matrix), you too can use keras::predict_classes on object$mannequin.

Utilizing a compiled Keras mannequin

This part reveals methods to enter a mannequin compiled within the trend typical to library(keras), which is helpful for extra superior fashions. Right here is an instance for lstm analogous to the imbd with Keras instance.

ok <- keras_model_sequential()
ok %>%
  layer_embedding(input_dim = reputation$P, output_dim = reputation$P) %>% 
  layer_lstm(items = 512, dropout = 0.4, recurrent_dropout = 0.2) %>% 
  layer_dense(items = 256, activation = "relu") %>%
  layer_dropout(0.3) %>%
  layer_dense(items = 8, # variety of ranges noticed on y (end result)  
              activation = 'sigmoid')

ok %>% compile(
  loss = 'categorical_crossentropy',
  optimizer = 'rmsprop',
  metrics = c('accuracy')
)

popularity_lstm <- kms(pop_input, rstats, ok)

Drop me a line through the mission’s Github repo. Particular due to @dfalbel and @jjallaire for useful strategies!!