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https://github.com/cran/pracma
21 November 2023, 19:34:12 UTC
Revision 26e049d70b4a1c237987e260cba68f6a9413736c authored by Hans W. Borchers on 09 April 2019, 04:10:07 UTC, committed by cran-robot on 09 April 2019, 04:10:07 UTC 
version 2.2.5
1 parent bf07673
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Tip revision: 26e049d70b4a1c237987e260cba68f6a9413736c authored by Hans W. Borchers on 09 April 2019, 04:10:07 UTC
version 2.2.5
Tip revision: 26e049d
circlefit.R 
##
##  c i r c l e f i t . R  Fitting a Circle
##


circlefit <- function(xp, yp, fast = FALSE) {
    if (!is.vector(xp, mode="numeric") || !is.vector(yp, mode="numeric"))
        stop("Arguments 'xp' and 'yp' must be numeric vectors.")
    if (length(xp) != length(yp))
        stop("Vectors 'xp' and 'yp' must be of the same length.")

    n  <- length(xp)
    p <- qr.solve(cbind(xp, yp, 1), matrix(xp^2 + yp^2, ncol = 1))
    r <- c(p[1]/2, p[2]/2, sqrt((p[1]^2 + p[2]^2)/4 + p[3]))

    cerr <- function(v)
        sqrt(sum((sqrt((xp - v[1])^2 + (yp - v[2])^2) - v[3])^2)/n)

    if (fast) {
        cat("RMS error:", cerr(r), "\n")
    } else {
        q <- optim(p, cerr)
        cat("RMS error:", q$value, "\n")
        r <- q$par
    }
    return(r)
}
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