# data visualization – How to build a trendline on a graph in R

## data visualization – How to build a trendline on a graph in R

since you had some data points missing, I took what you had provided: the six points.

edit – now the full example was available

1. A trendline is just a regression, and regressions are run most simple way like this:
`a<-lm(outcome~predictor)` — in this example the object a will hold your regression parameters. To get the values of your new trendline model, just use `predict(model_name)`, or in your case `predict(a)`

2. Adding line to a plot is dead simple. Just say `lines(b)`, where b specifies the line you want to plot after you have used the `plot()` function.

To wrap it up:

``````[![myds <- c(23.0415,13.1965,10.4110,12.2560,9.5910,10.7160,9.9665,8.5845,8.9855,8.8920,10.3425,9.3820,9.0860,9.6870,8.5635,9.0755,8.5960,7.9485,8.3235,8.1910)
x <- (1:length(myds))
plot(myds)

#make the main plot
plot(x,myds,ylim=c(5,30),xlim=c(0,20))

lines(predict(lm(myds~x)),col=green)

#one more trend
lines(predict(lm(myds~log(x))),col=red)][1]][1]
``````

Since you have not provided reproducible examples, Ill post some links, which I think might help you:

An example for a simple, linear trend line is here:
http://www.r-tutor.com/elementary-statistics/quantitative-data/scatter-plot

Furthermore, there has been a thread on this over at SO:
How do I add different trend lines in R?

Using ggplot would make it a bit easier, as you can use the smooth functions.