muscle

0th

Percentile

The purpose of this experiment was to assess the influence of calcium in solution on the contraction of heart muscle in rats. The left auricle of 21 rat hearts was isolated and on several occasions a constant-length strip of tissue was electrically stimulated and dipped into various concentrations of calcium chloride solution, after which the shortening of the strip was accurately measured as the response.

Keywords
datasets
Usage
muscle
Format

This data frame contains the following columns:

Strip
which heart muscle strip was used?
Conc
concentration of calcium chloride solution, in multiples of 2.2 mM.
Length
the change in length (shortening) of the strip, (allegedly) in mm.

References

Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth Edition. Springer.

Aliases
  • muscle
Examples
library(MASS) A <- model.matrix(~ Strip - 1, data=muscle) rats.nls1 <- nls(log(Length) ~ cbind(A, rho^Conc), data = muscle, start = c(rho=0.1), algorithm="plinear") (B <- coef(rats.nls1)) st <- list(alpha = B[2:22], beta = B[23], rho = B[1]) (rats.nls2 <- nls(log(Length) ~ alpha[Strip] + beta*rho^Conc, data = muscle, start = st)) Muscle <- with(muscle, { Muscle <- expand.grid(Conc = sort(unique(Conc)), Strip = levels(Strip)) Muscle$Yhat <- predict(rats.nls2, Muscle) Muscle <- cbind(Muscle, logLength = rep(as.numeric(NA), 126)) ind <- match(paste(Strip, Conc), paste(Muscle$Strip, Muscle$Conc)) Muscle$logLength[ind] <- log(Length) Muscle}) lattice::xyplot(Yhat ~ Conc | Strip, Muscle, as.table = TRUE, ylim = range(c(Muscle$Yhat, Muscle$logLength), na.rm = TRUE), subscripts = TRUE, xlab = "Calcium Chloride concentration (mM)", ylab = "log(Length in mm)", panel = function(x, y, subscripts, ...) { panel.xyplot(x, Muscle$logLength[subscripts], ...) llines(spline(x, y)) })
Documentation reproduced from package MASS, version 7.3-47, License: GPL-2 | GPL-3

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