# Analysis of community ecology data in R

David Zelený

### Others

This is an old revision of the document!

Author: David Zelený

The function uses aspect, slope and latitude of the plot and calculates heat load or radiation according to equations published by Keon & McCune (2002).

First version of the function not completely finished and debugged.

```# Function p.adjust.envfit
# Calculates adjusted P values for results stored in envfit object,
# created using envfit function from vegan, which fits supplementary variables
# onto axes of unconstrained ordination.
# Arguments:
# aspect - aspect of the plot, vector.
# slope - inclination of the plot, vector.
# latitude - latitude of the plot, either vector of the same length as aspect or slope, or single value (in case that all plots are from the same relatively small region)
# method - default is "heatload", alternative is "radiation".
# units - default id "degrees", alternative is "radians".
# equation - the number of equation (1, 2 or 3); default is 3.
# Author: David Zeleny
heatload <- function (aspect, slope, latitude, method = 'heatload', units = 'degrees', equation = 3)
{
if (units == 'degrees'){# convert degrees to radians
aspect <- aspect/180*pi
slope <- slope/180*pi
aspect[slope == 0] <- 0
latitude <- latitude/180*pi
}
A <- if (method == 'heatload') abs (pi - abs (aspect - (5*pi/4))) else pi - abs (aspect-pi)
S <- slope
L <- if (length (latitude) == 1) rep (latitude, length (A)) else latitude
if (equation == 1) res <- exp (-1.467 +1.582*cos(L)*cos(S) -1.500*cos(A)*sin(S)*sin(L) -0.262*sin(A)*sin(S) +0.607*cos(A)*sin(S))
if (equation == 2) res <- exp (-1.236 +1.350*cos(L)*cos(S) -1.376*cos(A)*sin(S)*sin(L) -0.331*sin(A)*sin(S) +0.375*cos(A)*sin(S))
if (equation == 3) res <-      +0.339 +0.808*cos(L)*cos(S)                             -0.196*sin(A)*sin(S) +                    - 0.482*cos(A)*sin(S)
return (res)
}```

Example of the use on the dataset `grasslands.env` (acidophilous grasslands in Trebic region, Czech Republic). The `grasslands.env` contains variables `aspect`, `slope` and `latitude`, all in degrees. Dataset represents small plots (16-25m2) located on convex outcrops in the agricultural landscape, covered by seminatural grassland vegetation.

```source ('http://anadat-r.davidzeleny.net/doku.php/en:customized_functions:heatload?do=export_code&codeblock=0') # reads the function definition from above