majom - 1 year ago 66

R Question

I have a problem using

`loess`

`loess.smooth`

Both commands don't work with this toy data.

`x <- as.Date(c(1, 2, 4, 5, 6), origin="2010-1-1")`

y <- c(4, 8, 8, 28, 11)

plot(x, y, ylim=c(1,30))

lines(loess(y ~ x), col="red")

lines(loess.smooth(y=y, x=x), col="blue")

Answer Source

I ended up using the following code:

```
# Data
x.1 <- as.Date(c(1, 2, 4, 5, 6), origin="2010-1-1")
x.2 <- c(1, 2, 4, 5, 6)
y <- c(4, 8, 8, 28, 11)
# x.2 - x is numeric variable
plot(x.2, y, ylim=c(1,30))
lines(loess(y ~ x.2, span=1.01), col="black", lwd=2, lty=2) # neccessary to change span default to avoid warnings (span = 0.75)
lines(loess.smooth(x.2, y, span=1.01), col = "orange", , lwd=2) # neccessary to change span default to avoid warnings (span = 2/3)
lines(smooth.spline(x.2,y), col="blue", lwd=2)
# x.1 - x is date variable
plot(x.1, y, ylim=c(1,30))
# loess() cannot deal with date variables, thus convert it to
lines(loess(y~as.numeric(x.1), span=1.01), col="red", lwd=2) # neccessary to change span default to avoid warnings (span = 0.75)
lines(loess.smooth(x.1, y, span=1.01), col = "orange", lwd=2) # neccessary to change span default to avoid warnings (span = 2/3)
lines(smooth.spline(x.1,y), col="blue", lwd=2)
```

The problems were:
(1) `loess`

is unable to deal with date variables.
(2) The `span`

parameter had to be adjusted (>1).