# Why the Logistic regression model trained with tensorflow performed so poor

I trained a logistic regression model with tensorflow but the accuracy of the model was so poor (accuracy = 0.68). The model was trained using simulated dataset and the result should be very good. is there something wrong with the code ?

 #simulated dataSet
sim_data <- function(n=2000){
library(dummies)
age <- round(abs(rnorm(n,mean = 60, sd = 20)))
lac <- round(abs(rnorm(n,3,1)),1)
wbc <- round(abs(rnorm(n,10,3)),1)
sex <- factor(rbinom(n,size = 1,prob = 0.6),
labels = c("Female","Male"));
type <- as.factor(sample(c("Med","Emerg","Surg"),
size = n,replace = T,
prob = c(0.4,0.4,0.2)))
linPred <- cbind(1,age,lac,wbc,dummy(sex)[,-1],
dummy(type)[,-1]) %*%
c(-30,0.2,4,1,-2,3,-3)
pi <- 1/(1+exp(-linPred))
mort <- factor(rbinom(n,size = 1, prob = pi),
labels = c("Alive","Died"))
dat <- data.frame(age=age,lac=lac,wbc=wbc,
sex=sex,type=type,
mort = mort)
return(dat)
}
set.seed(123)
dat <- sim_data()
dat_test <- sim_data(n=1000)
#logistic regression in conventional method
mod <- glm(mort~.,data = dat,family = "binomial")
library(tableone)
ShowRegTable(mod)
#diagnotic accuracy
pred <- predict.glm(mod,newdata = dat_test,
type = "response")
library(pROC)
roc(response = dat_test$$mort,predictor = pred,ci=T) predBi <- pred >= 0.5 crossTab <- table(predBi,dat_test$$mort)
(crossTab+crossTab)/sum(crossTab)
#choose different cutoff for the accuracy
DTaccuracy <- data.frame()
for (cutoff in seq(0,1,by = 0.01)) {
predBi <- pred >= cutoff;
crossTab <- table(predBi,dat_test$mort) accuracy = (crossTab+crossTab)/sum(crossTab) DTaccuracy <- rbind(DTaccuracy,c(accuracy,cutoff)) } names(DTaccuracy) <- c('Accuracy','Cutoff') qplot(x=Cutoff, y = Accuracy, data = DTaccuracy) #tensorflow method library(caret) y = with(dat, model.matrix(~ mort + 0)) x = model.matrix(~.,dat[,!names(dat)%in%"mort"]) trainIndex = createDataPartition(1:nrow(x), p=0.7, list=FALSE,times=1) x_train = x[trainIndex,] x_test = x[-trainIndex,] y_train = y[trainIndex,] y_test = y[-trainIndex,] # Hyper-parameters epochs = 30 # Total number of training epochs batch_size = 30 # Training batch size display_freq = 10 # Frequency of displaying the training results learning_rate = 0.1 # The optimization initial learning rate #Then we will define the placeholders for features and labels: library(tensorflow) X <- tf$$placeholder(tf$$float32, shape(NULL, ncol(x)), name = "X") Y = tf$$placeholder(tf$$float32, shape(NULL, 2L), name = "Y") #we will define the parameters. We will randomly initialize the weights with mean “0” and a standard deviation of “1.” We will initialize bias to “0.” W = tf$$Variable(tf$$random_normal(shape(ncol(x),2L), stddev = 1.0), name = "weghts") b = tf$$Variable(tf$$zeros(shape(2L)), name = "bias") #Then we will compute the logit. logits = tf$$add(tf$$matmul(X, W), b) pred = tf$$nn$$sigmoid(logits) #The next step is to define the loss function. We will use sigmoid cross entropy with logits as a loss function. entropy = tf$$nn$$sigmoid_cross_entropy_with_logits(labels = Y, logits = logits) loss = tf$reduce_mean(entropy,name = "loss")
#The last step of the model composition is to define the training op. We will use a gradient descent with a learning rate 0.1 to minimize cost.

optimizer = tf$$train$$GradientDescentOptimizer(learning_rate = learning_rate)$$minimize(loss) init_op = tf$$global_variables_initializer()
#Now that we have trained the model, let’s evaluate it:

correct_prediction <- tf$$equal(tf$$argmax(logits, 1L), tf$$argmax(Y, 1L), name = "correct_pred") accuracy <- tf$$reduce_mean(tf$$cast(correct_prediction, tf$$float32),
name = "accuracy")
#Having structured the graph, let’s execute it:

with(tf$$Session() %as% sess, { sessrun(init_op) for (i in 1:5000) { sessrun(optimizer, feed_dict = dict(X=x_train, Y=y_train)) } sess$$run(accuracy,
feed_dict=dict(X = x_test, Y = y_test))
})


The accuracy obtained by glm() method is quite good (accuracy=0.95), which is as expected; however, the accuracy was only 0.68 with TensorFlow method. How can I solve the problem?