# Tips on using R

## Writing text to the clipboard

I just realized that this is really easy as there exists in R function `writeClipboard()` that copies character strings to the Windows clipboard!

```writeClipboard("Hello")
writeClipboard(as.character(1:10))
writeClipboard(sprintf("%.2f degrees", 1:10))```

For the reverse operation of reading from the clipboard, two functions are available `getClipboardFormats()` and `readClipboard()`.

## Test of significance of linear regression slope

The examples below are for the common cases of a null hypothesis of slope = 0 and slope = 1, but it should be clear how to test for for any arbitrary constant slope value expected a priori of examination of the data. The examples use a one-sided test, in many cases, a two-sided test should be used (e.g. if there is no a priori expectation of the deviation from the null hypothesis to be possible only in one direction). Source unknown, but certainly not of my authorship.

```# cars data from R for this example
data(cars)
# linear regression fit
cars.lm <- lm(dist ~ speed, data = cars)
# extract slope estimate and its s.e. indexing by explanatory variable name
my.slope <- summary(cars.lm)\$coef["speed", c("Estimate", "Std. Error")]
# extract degrees of freedom
my.df <- summary(cars.lm)\$df
# test against hypothesis of no response, i.e. slope = 0
t_value_zero <- my.slope["Estimate"] / my.slope["Std. Error"]
dt(t_value_zero, df = my.df) / 2 # one sided test
# test against hypothesis of 1:1 relationship, i.e. slope = 1
t_value_one <- (my.slope["Estimate"] - 1) / my.slope["Std. Error"]
dt(t_value_one, df = my.df) / 2 # one sided test```
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