Non-numeric argument to binary operator, CSV - r

Question

I've seen that other people before were already struggling with this, however I didn't manage to solve my problem with those posts. I get the error 'Non-numeric argument to binary operator'. The following reproducible example works:
x=rnorm(1000)+sin(c(1:1000)/100)#random data+ sinus superimposed
par(mfrow=c(2,2))
plot(x)# plot random data
plot(filter(x,rep(1/100,100)))
plot(x-filter(x,rep(1/100,100)))
# variances of variable, long term variability and short term variability
var(x)
var(filter(x, rep(1/100,100)),na.rm=T)
var(x-filter(x, rep(1/100,100)),na.rm=T)
However, I of course want to use my own dataset, it's a csv, and this is when the error occurs. It must have something to do with the data format, because when I export the random data to csv:
x=rnorm(1000)+sin(c(1:1000)/100)#random data+ sinus superimposed
write.csv(x,"dat.csv")
and then try to read in dat.csv
y <- read.csv("dat.csv", header=TRUE, stringsAsFactors=FALSE)
par(mfrow=c(2,2))
plot(y)
plot(filter(y,rep(1/100,100)))
plot(y-filter(y,rep(1/100,100)))
[...] I get the error
Error in x - filter(x, rep(1/100, 100)) :
non-numeric argument to binary operator
Calls: plot
In addition: Warning message:
In plot(x - filter(x, rep(1/100, 100))) :
Incompatible methods ("Ops.data.frame", "Ops.ts") for "-"
Execution halted
Why are the values not numeric? I don't get it. Thanks for your help!

Answer 1

I rewrote the post a little so the x variable wasn't reused for the input & output. The value from read.csv() is now y. Notice its a data.frame, while x is an ordinary numeric vector.
To get the 2nd set of graphs to behave like the first set, extract the first vector from y (called y1 below), then pass that vector to the dplyr functions.
y <- read.csv("dat.csv", header=TRUE, stringsAsFactors=FALSE)
y1 <- y$x # Extract the first column
par(mfrow=c(2,2))
plot(y1)
plot(filter(y1,rep(1/100,100)))
plot(y1-filter(y1,rep(1/100,100)))