CODEWITHSUNDEEP
rplotggplot2statistics
Victor Espinoza
Victor Espinoza

Reputation: 338

error using qplot with facets?

I am trying to do a histogram with this data for an example of using ggplot2 to create graphics, and then i found out i cant do this histogram with facets using qplot command, i already do this kind of plot with another data, but now i trying again with this specific data i can not do it.

this is the code:

library(ggplot2)
qplot(x      = diamonds$price,
      geom   = "histogram",
      facets = .~diamonds$cut)

As you can see is actually really simple but it give me the error:

Error: value for ‘cut’ not found

if you do a quick research you find out that there are price values for every level in the cut factor.

diamonds$price[diamonds$cut=="Fair"]
diamonds$price[diamonds$cut=="Good"]
diamonds$price[diamonds$cut=="Very Good"]
diamonds$price[diamonds$cut=="Premium"]
diamonds$price[diamonds$cut=="Ideal"]

i couldn't understand what is wrong.

this is another example. But this is working.

x <- rnorm(120,20,20)
y <- as.factor(c(rep("yo",60),rep("tu",60)))
df <- data.frame(x,y)
qplot(x = df$x, geom = "histogram", facets = .~df$y)

What is the different between this data? i can not see it.

This show me that variables class are the same in this two example

is.numeric(diamonds$price)

[1] TRUE

is.numeric(x)

[1] TRUE

is.factor(diamonds$cut)

[1] TRUE

is.factor(y)

[1] TRUE

Please help.

Upvotes: 0

Views: 728

Answers (1)

Victor Espinoza
Victor Espinoza

Reputation: 338

The following answer is based in aosmith help, thanks.

The problem is that qplot is actually not reading the df$x and df$y variables in example number 2:

library(ggplot2)    
x <- rnorm(120,20,20)
y <- as.factor(c(rep("yo",60),rep("tu",60)))
df <- data.frame(x,y)
qplot(x = df$x, geom = "histogram", facets = .~df$y)

In this example, qplot is readind the object x and y, created in the first two lines, it never use df$x or df$y.

So, in the example number 1:

qplot(x      = diamonds$price,
      geom   = "histogram",
      facets = .~diamonds$cut)

There is not price or cut object in the environment, that is why i get the error.

Solution: Using the argument data =

like this:

qplot(data = diamonds,
      x = price,
      geom = "histogram",
      facets = .~cut)

Upvotes: 1

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