Martin Biuw wrote:
Hi,
Sorry if this is an obvious one, but is there a simple way to modify the lm function to test whether a slope coefficient is significantly different from 1 instead of different from 0?
Thanks,
There might be an easier way, but the brute force method would be:
R> set.seed(1) R> x <- data.frame(x = 1:10, y = 1:10 + rnorm(10)) R> lm.x <- lm(y ~ x, data = x) R> coef.x <- summary(lm.x)$coef R> # t-statistic comparing slope to 1 R> t.x <- (coef.x["x","Estimate"]-1)/coef.x["x","Std. Error"] R> # p-value R> 2 * pt(abs(t.x), lm.x$df, lower = FALSE) [1] 0.5559868
Hope this helps,
Sundar
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