Logarithmic scale - Histogram R

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I plotted a chart of type histogram, using the following code:

hist(dados1$Prec, breaks=40 , col=rgb(0.2,0.8,0.5,0.5) , border=F , main="" , xlab="Precipitação (mm)", xlim=c(0,140), ylim = c(0,10000))

I need to place the histogram in logarithmic scale so that the other classes (bars) can also appear, due to the large amount of values I have. How could I do that?

Follow the sample of my data:

dput(head(dados1$Prec,500))
c(8.9, 32.7, 0.3, 3.9, 8.8, 29.2, 2.5, 0.6, 27.7, 11.2, 9.8, 
0, 6.6, 0, 0, 0, 0, 0, 5.5, 0, 0, 0, 0, 6.2, 0, 0, 19.4, 15.1, 
0.9, 16.4, 0, 0, 0, 0, 0, 0, 0, 0.1, 10.1, 0.1, 0.2, 1.3, 2.4, 
2.6, 0, 0, 4.8, 0, 0.6, 7.1, 4.1, 0, 5, 0, 2.3, 6.3, 9.1, 25.7, 
8.3, 24, 1.2, 0, 0, 0, 0, 19.8, 5.5, 0, 0, 0, 0.2, 0, 2.8, 6.9, 
51.6, 41.6, 58.9, 0.2, 0, 22.1, 0, 0, 2.3, 0, 2.2, 10.6, 0, 0, 
0, 0, 0, 0.3, 0, 4, 0, 0.2, 0, 13.7, 0.7, 44.6, 0, 0, 0, 0, 20.2, 
0, 1.3, 0, 0.7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 31.5, 
0, 6.8, 0, 0, 6.8, 11.6, 5.4, 1.8, 0, 0, 0.9, 0, 7.6, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0.4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0.1, 0, 0, 0, 0, 0.5, 0.1, 3.1, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3.1, 0.5, 0, 0, 0, 
0, 0.1, 3.6, 14.2, 0, 6.6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.2, 
2.1, 0, 0, 0, 0, 0, 0, 0, 9.2, 12.6, 0, 0, 0, 0, 0, 1.2, 26.2, 
8, 0.5, 0, 0, 5.8, 0, 0, 0, 0, 0, 0, 9.2, 0, 0, 30.9, 0, 4.1, 
1.6, 3.6, 10.7, 0, 0.5, 0, 31.5, 0, 6.6, 0.1, 2.8, 0, 0, 0, 2.4, 
0, 14.2, 0, 13.5, 0.2, 12.9, 3.8, 0, 0, 93.2, 0, 0, 0, 0, 0, 
0, 1.4, 0.3, 38.6, 0, 14.3, 0.3, 0.2, 0, 6.2, 40.4, 1.1, 0, 1.2, 
0, 0, 0, 0, 0, 1.5, 1.6, 5.6, 0, 12.6, 0.3, 7, 35.6, 0.6, 0, 
0, 5.5, 0, 0.5, 0, 16.3, 33.6, 46.8, 35, 0, 0, 0, 13.2, 0.9, 
0.2, 0, 46.2, 0, 0, 2.8, 3.6, 20.1, 9.3, 16.3, 11.1, 0, 0.1, 
0.6, 27.9, 14.9, 22.1, 5.7, 0, 2.4, 9.4, 0.5, 0, 24.4, 0, 6.3, 
7.2, 15.4, 0.8, 0, 50.1, 4, 18.6, 0.8, 0.2, 25.3, 16.6, 0.9, 
0, 0.1, 2.4, 0.4, 0, 0, 5.3, 0, 39.8, 0, 22.5, 5.8, 2.7, 0, 9.2, 
23.6, 0, 0, 0, 51.7, 0, 10.7, 33.5, 24.6, 4, 0, 3.1, 5.9, 38.4, 
0, 0, 0, 0, 0, 25.7, 0, 7, 0, 7.6, 0, 0.2, 2.3, 0.2, 18.3, 32, 
10.2, 32.3, 2.2, 1, 14.3, 1.7, 0.8, 11.4, 0.3, 0, 0, 43, 0, 12.2, 
2.8, 0, 0, 34.3, 32.1, 2, 0, 0, 9.9, 0.3, 11.2, 2, 5.3, 4.3, 
1.2, 0, 0, 7.8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0)
r

2 answers

3


Histogram is a bar graph with the element count by range. You can calculate the information with the function hist and use barplot to generate the chart with adjustments:

histPrec <- hist(dados1$Prec, breaks = 40, plot = FALSE)

The bar graph of histPrec$counts will be the same as the histogram of dados1$Prec:

par(mfrow = c(1,2))
hist(dados1$Prec, breaks = 40)
barplot(histPrec$counts, space = 0)
axis(1, at = 0:length(histPrec$counts), labels = histPrec$breaks)

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To set the axis to log scale, just use the option log. But as there are intervals that have count 0, will return error. You can handle this in a few ways: 1) plot log(Counts) and not turn the axis; 2) use Counts+1; 3) replace counts 0 with NA.

counts.sem.zero <- histPrec$counts
counts.sem.zero[counts.sem.zero == 0] <- NA

par(mfrow = c(1,3))
barplot(log(histPrec$counts), ylim = c(0, log(max(histPrec$counts))), ylab = "log(frequência)")
barplot(histPrec$counts+1, log = "y", ylim = c(1, max(histPrec$counts+1)), ylab = "frequência + 1")
barplot(counts.sem.zero, log = "y", ylab = "frequência")

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I recommend the latter, since there is no change in values, which makes the interpretation of the Y axis more direct.

  • Carlos Eduardo, I need the values that are zero "0" to be accounted for, in this case they cannot be considered NA. I would have some suggestion about that?

  • I edited the answer to include other options, but I recommend replacing zeros with NA. The exchange is done in the data to plot the histogram, does not change the original date.frame.

  • Carlos Eduardo, thank you so much for your help so far! I edited my question to show you how was my histogram with the change made and unfortunately I could not understand what the problem occurs in my code. One question is whether, in this case, the values "0" are being counted in the first bar of the histogram, as the intervals between the classes do not appear.

  • 1

    You used the raw data, not the count generated by hist. The shaft can be added with axis, as in my first example. I did not put in the second to make the example cleaner.

1

You can define a function that calls first hist with plot = FALSE in order to obtain the count vector. If counts == 0 they are given the value NA not to appear on the chart. So R does not compute the logarithms of 0. Finally, it is used barplot to plot the graph.

hist_logy <- function(x, breaks = "Sturges", plot = TRUE, ...){
  h <- hist(x, breaks = breaks, plot = FALSE)
  is.na(h$counts) <- h$count == 0
  if(plot) barplot(setNames(h$counts, h$mids), log = "y", space = 0, ...)
  invisible(h)
}

hist_logy(x)

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hist_logy(x, breaks = "FD", col = "cyan")

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