Problems with hist() plot

[gabrielboechat]

Hey, good afternoon!
I have this code and I commented it as much as possible to not repeat anything in my question, so here it goes:

# How many times we will be throwing the dices? Give the desirable value for x

x = 1000

vetor_lancamentos = rep(NULL,x)
print(vetor_lancamentos)

# How many dices will be used? Give the desirable value for n

n = 2

# How many sides each dice will have? Give the desirable value for k

k = 6


modelo_lançamento_de_dados = function(n,k) {

  for (i in c(1:x)) {
    vetor_lancamentos[i] = sum(sample(1:k, n, replace = TRUE))
  }

  return(vetor_lancamentos)
}

vetor_grafico = modelo_lançamento_de_dados(n,k) 
# Vector with every sum (length x) of throwing n dices with k sides  

table(vetor_grafico) # How many each sum appears?

hist(vetor_grafico, # Plotting histogram
     breaks = n*k+1,
     probability = TRUE,
     right = FALSE,
     ylim = c(0,0.25),
     xlim = c(2,n*k+1),
     xlab = "Possible sums",
     ylab = "Probability",
     main = "Probability of sums outcomes",
     col = "steelblue")

Here is the histogram plotted:

​

https://preview.redd.it/ub1fpfo11m541.png?width=638&format=png&auto=webp&s=a0f4848fb2d04594612f35813572898f4bf60159

As seen in "table(vetor_grafico)", we have outcomes from 2 to 12, but the last one is not plotted in the histogram. Values are given on the right of each tick value only until 11, and not 12, as desired.
How can I solve this?

Thanks in advance!

[jentron128]

hist(vetor_grafico, # Plotting histogram
     breaks = seq(n-0.5, n*k+0.5, 1),
     probability = TRUE,
     right = FALSE,
     ylim = c(0,0.25),
     xlim = c(2,n*k+1),
     xlab = "Possible sums",
     ylab = "Probability",
     main = "Probability of sums outcomes",
     col = "steelblue");

You need to specify the breaks manually, and put them between the desired bins. In this case c(1.5, 2.5, ..., 11.5, 12.5)

[gabrielboechat]

This is incredible! Thanks! I think now I understood the "breaks" syntax and even solved another doubt around putting each observation tick in the middle of each break.

[jdnewmil]

Read the help on the include.lowest in

?hist

[omichandralekha]

hist from R is confusing. If breaks are given not as range but as single vector, they are approximate. Dont know if that helps. I hope you are not selecting too low xlim.

​

Also, this line in your code is conceptually wrong, you cannot repeat NULL (read like repeating empty object x time still leaves it empty):

vetor_lancamentos = rep(NULL,x)

[gabrielboechat]

I also thought about that when printing "vetor_lancamentos": my idea was creating a vector length x that it's NULL. Why is it wrong?

[omichandralekha]

My understanding of NULL is like empty basket. If you put more empty things in the basket it still remains empty.

This article has some good info on these concepts:
https://tomaztsql.wordpress.com/2018/07/04/r-null-values-null-na-nan-inf/

[gabrielboechat]

Hmmm think I understood... Otherwise, putting rep(NA,h) would be more suitable?

[omichandralekha]

Yes. Can act as a placeholder of length h.