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Greets, I'm trying to use nlminb() to estimate the parameters of a bivariate normal sample and during one of the iterations it passes a parameter vector to the likelihood function resulting in an invalid covariance matrix that causes dmvnorm() to throw an error. Thus, it seems I need to somehow communicate to nlminb() that the final three parameters in my parameter vector are used to

Greets, I'm trying to learn to use nls and was running the example code for an exponential model: > x <- -(1:100)/10 > y <- 100 + 10 * exp(x / 2) + rnorm(x)/10 > nlmod <- nls(y ~ Const + A * exp(B * x)) Error in B * x : non-numeric argument to binary operator In addition: Warning message: In nls(y ~ Const + A * exp(B * x)) : No starting values specified for some

Greets, I'm using a data frame that looks like: > head(pr2) X1 X2 X3 X4 Y fit res 1 44 33.2 5 30 41.2 39.22201 1.977991 2 43 33.8 4 41 31.7 38.48476 -6.784761 3 48 40.6 3 38 39.4 44.78278 -5.382783 4 52 39.2 7 48 57.5 51.48134 6.018656 5 71 45.5 11 53 74.8 68.25585 6.544153 6 44 37.5 9 65 59.8 53.27743 6.522569 Along with the command: >

Greets, My data looks like: > p3.18 s xbar subgroup 1 0.84 12.2 1 2 1.64 11.2 2 3 2.07 10.6 3 4 2.49 12.2 4 5 0.84 11.2 5 ... Using the command > qcc(p3.18$xbar,type="xbar",sizes=5,center=mean(p3.18$xbar),std.dev=mean(p3.18$s)/0.94,title="X-bar Chart for Paper Sheet Length Data") I get the x-bar chart I expect. However,