remove some rows in dataframe

Question

I have a data frame:

mydata <- data.frame(
  x1= as.factor(1:3), 
  x2= as.factor (4:6), 
  x3= as.factor(7:9), 
  x4= as.factor (2:7), 
  x5= as.factor(1:6), 
  x6= seq(0,600,len= 600),
  x7= seq(0,1,len=600)
  )

And I want to remove some rows in this with particular conditions. I did it this way:

mydata1 <- mydata%>%
filter(x1==1, x2==4, x3==7, x4==2, x5==1)%>%
anti_join(mydata,., by=c("x1", "x2", "x3", "x4","x5","x6" "x7"))

mydata2 <- mydata1%>%
filter(x1==3, x2==6 x3==9, x4==7, x5==6)%>%
    anti_join(mydata1,., by=c("x1", "x2", "x3", "x4","x5","x6", "x7"))

There are a lot of rows that I want to remove. Is there another way to do this?

Why are you using factors here? Factors with integer levels that don't correspond to the level numbers seem like a risky and unnecessary complication. — Gregor Thomas
– Gregor Thomas, Commented Oct 29, 2016 at 8:52
A base R option is mydata1 <- mydata[!as.character(interaction(mydata[1:5])) %in% "1.4.7.2.1",];mydata2 <- mydata1[!as.character(interaction(mydata1[1:5])) %in% "1.6.9.7.6",] — akrun
– akrun, Commented Oct 29, 2016 at 8:57

Gregor Thomas · Accepted Answer · 2016-10-29 09:00:21Z

2

You can combine logical tests with & for and and | for or. If you want to remove rows that meet all of the following

x1==1, x2==4, x3==7, x4==2, x5==1

Then do it like this:

filter(mydata, !(x1 == 1 & x2 == 4 & x3 == 7 & x4 == 2 & x5 == 1))

The row order is different, but the results are the same:

md1 = filter(mydata, !(x1 == 1 & x2 == 4 & x3 == 7 & x4 == 2 & x5 == 1))
identical(arrange(md1, x6), arrange(mydata1, x6))
# [1] TRUE

You can combine your conditions into one filter this way:

md2 = filter(
  mydata,
  !(x1 == 1 & x2 == 4 & x3 == 7 & x4 == 2 & x5 == 1),
  !(x1 == 3 & x2 == 6 & x3 == 9 & x4 == 7 & x5 == 6)
)

answered Oct 29, 2016 at 9:00

Gregor Thomas

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