R: Heart rate baroreflexes for rabbits

heartrate {drc} | R Documentation

## Heart rate baroreflexes for rabbits

### Description

The dataset contains measurements of mean arterial pressure (mmHG) and heart rate (b/min) for a baroreflex curve.

### Usage

    data(heartrate)

### Format

A data frame with 18 observations on the following 2 variables.

`pressure`

  a numeric vector containing measurements of arterial pressure.

`rate`

  a numeric vector containing measurements of heart rate.

### Details

The dataset is an example of an asymmetric dose-response curve, that is not easily handled using the log-logistic or Weibull models (`LL.4`, `LL.5`, `W1.4` and `W2.4`), whereas the `baro5` model provides a nice fit.

### Source

Ricketts, J. H. and Head, G. A. (1999) A five-parameter logistic equation for investigating asymmetry of curvature in baroreflex studies, Am. J. Physiol. (Regulatory Integrative Comp. Physiol. 46), 277, 441–454.

### Examples

    ## Fitting the baro5 model
    heartrate.m1 <- drm(rate~pressure, data=heartrate, fct=baro5())
    plot(heartrate.m1)

    coef(heartrate.m1)

    #Output:
    #b1:(Intercept) b2:(Intercept)  c:(Intercept)  d:(Intercept)  e:(Intercept)
    #      11.07984       46.67492      150.33588      351.29613       75.59392

    ## Inserting the estimated baro5 model function in deriv()
    baro5Derivative <- deriv(~ 150.33588 + ((351.29613 - 150.33588)/
    (1 + (1/(1 + exp((2 * 11.07984 * 46.67492/(11.07984 + 46.67492)) *
    (log(x) - log(75.59392 ))))) * (exp(11.07984 * (log(x) - log(75.59392)))) +
    (1 - (1/(1 + exp((2 * 11.07984 * 46.67492/(11.07984 + 46.67492)) *
    (log(x) - log(75.59392 )))))) * (exp(46.67492 * (log(x) - log(75.59392 )))))), "x", function(x){})

    ## Plotting the derivative
    #pressureVector <- 50:100
    pressureVector <- seq(50, 100, length.out=300)
    derivativeVector <- attr(baro5Derivative(pressureVector), "gradient")
    plot(pressureVector, derivativeVector, type = "l")

    ## Finding the minimum
    pressureVector[which.min(derivativeVector)]

[Package drc version 3.0-1 Index]