在R中绘制多个根

Question

I have an equation which I would like to solve for values of m

m^2+x*m+1=0

I know I can find these roots using polyroot(c(1,x,1)) .

I'd like to plot these roots in R for varying x such that all the real roots of the polynomial are plotted for each value of x .

Note, the polynomial may become more complex than this, ruling out application of the quadratic or cubic formulas.

Any thoughts as to how I could accomplish this?

Thanks!

Answer 1

I think this will do the trick. Just set X to whatever values you want to evaluate.

X <- seq(0, 10, length=21)
roots <- sapply(X, function(x) polyroot(c(1,x,1))) 
roots[abs(Im(roots)) > 1e-10] <- NA
matplot(X, t(roots), pch=1)