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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>Forestry Functions</title>
<link rel="Shortcut Icon" href="http://oak.snr.missouri.edu/sylvan/images/sylview-icon.ico">
<link rel="stylesheet" type="text/css" href="css/style.css" />
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']]}
});
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src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML">
</script>
</head>
<body>
<p></p>
<center>
<table border="0" width="90%">
<tbody>
<tr>
<td>
<table border="0">
<tbody>
<tr>
<td width="90%" align="left">
<div id="header" algin="left" class="bgcol" >
<h1 align="left" width="90%" style="margin-left:45px; color:white; font-size:38 ">Forest Functions, <small> Computer code to help foresters</small></h1></div>
<br/>
<h2>Basal area per acre</h2>
<p>Basal area per acre is the cross-section area of all the trees on an acre.
</p>
<p>
<center>
<font size="5">
$$ba = \sum_{i=1}^{n} 0.005454154 * dbh_i^2 * w_i$$
</font>
</center>
</p>
<p>
where $ba$ is the basal are per acre, 0.005454154 is a constant, $dbh$ is the diameter at breast height in inches,
and $w$ is the expansion factor that converts the sample tree to a per acre basis.
</p>
<p>
<center>
<font size="5">
$$ba = \sum_{i=1}^{n} 0.00007854 * dbh_i^2 * w_i$$
</font>
</center>
</p>
<p>
where $ba$ is the basal are per hectare, 0.00007854 is a constant, $dbh$ is the diameter at breast height in centimeters,
and $w$ is the expansion factor that converts the sample tree to a per hectare basis.
</p>
<h3>Example</h3>
<p>
<dl>
<dt><b>Imperial Units</b></dt>
<dd> dia = 8,6,8,5,4,6,7 in inches</dd>
<dd> weight = 10,10,10,10,10,10,10</dd>
<dd> unittype = "imperial"</dd>
<dd> Answer = 15.8 sq. feet per acre</dd>
</dl>
</p>
<p>
<dl>
<dt><b>Metric Units</b></dt>
<dd> dia = 8,6,8,5,4,6,7 in centimeters</dd>
<dd> weight = 25,25,25,25,25,25,25</dd>
<dd> unittype = "metric"</dd>
<dd> Answer = 0.56 sq. meters per hectare</dd>
</dl>
</p>
<h3>Code</h3>
<h4>Visual Basic</h4>
<p>
<div style="background-color:lightgrey;border:1px solid black;padding 10px">
<pre> <code>
Function basalarea(dbh As Range, w As Range, Optional unittype As String = "imperial") As Double
' Function to calculate basal area per acre from diameter at breast height and expansion factor weights
' by David R. Larsen, Copyright October 10, 2012
' Creative Commons http://creativecommons.org/licenses/by-nc/3.0/us/
If (unittype = "imperial") Then
For i = 1 To dbh.Height
basalarea = basalarea + 0.005454154 * dbh(i).Value ^ 2 * w(i).Value
Next i
ElseIf (unittype = "metric") Then
For i = 1 To dbh.Height
basalarea = basalarea + 0.00007854 * dbh(i).Value ^ 2 * w(i).Value
Next i
Else
basalarea = 0#
MsgBox ("Unknown unit type, options are: imperial or metric")
End If
End Function
</code></pre>
</div>
<a href="https://github.com/LarsenDR/forfuncVBS/blob/master/VBS/basalarea.vbs">Excel® Visual Basic Code</a><br/>
</p>
<h4>R Statistical Package Code</h4>
<p>
<div style="background-color:lightgrey;border:1px solid black;padding 10px">
<pre> <code>
basalarea = function( dia, weight, unittype="imperial" )
{
# Function to calculate the basal area per unit area
# weight is the expansion factor to convert the sample area number to
# the unit area.
# By David R. Larsen, Copyright, October 9, 2012
# Creative Commons http://creativecommons.org/licenses/by-nc/3.0/us/
if ( unittype == "imperial" ){
bat = 0.005454154 * dia ^ 2 * weight
}else if ( unittype == "metic" ){
bat = 0.00007854 * dia ^ 2 * weight
}else{
bat = rep( 0, length=length(dia) )
}
ba = sum(bat)
ba
}
</code></pre>
</div>
<a href="https://github.com/LarsenDR/forfuncR/blob/master/R/basalarea.R">R Statistical Package Code</a><br/>
</p>
<h4>Python Code</h4>
<p>
<div style="background-color:lightgrey;border:1px solid black;padding 10px">
<pre> <code>
#!/usr/local/bin/python
# Function to calculate the basal area per acre
# from diameter and weight
# by David R. Larsen, October 11, 2012
# Creative Commons, http://creativecommons.org/licenses/by-nc/3.0/us/
def basalarea( dia=[], weight=[], unittype="imperial"):
idx = 1
value = 0
for d in dia:
if( unittype == "imperial" ):
value = value + 0.005454154 * d**2 * weight[idx]
elif( unittype == "metric"):
value = value + 0.00007854 * d**2 * weight[idx]
else:
print "Unknown unittype, options are imperial or metric"
return
idx = idx + 1
next
return value
print "basalarea =", basalarea(dia=[8,6,8,5,4,6,7],weight=[10,10,10,10,10,10,10] )
print "basalarea =", basalarea(dia=[8,6,8,5,4,6,7],weight=[10,10,10,10,10,10,10], unittype="imperial" )
print "basalarea =", basalarea(dia=[8,6,8,5,4,6,7],weight=[25,25,25,25,25,25,25], unittype="metric" )
print "basalarea =", basalarea([1], [1], "cunits")
</code></pre>
</div>
<a href="https://github.com/LarsenDR/forfuncPython/blob/master/python/basalarea.py">Python Code</a>
</p>
<p>
Note the python file has a extra "txt" at the end to allow the files to be viewed in a web browser.
</p>
<h4> Go Code</h4>
<p>
<div style="background-color:lightgrey;border:1px solid black;padding 10px">
<pre> <code>
// Function to calculate the basal area per acre
// from diameter and weight
// by David R. Larsen, November 20, 2013
// Creative Commons, http://creativecommons.org/licenses/by-nc/3.0/us/
package main
import (
"fmt"
)
func basalarea(dia []float64, wt []float64, unittype string) (ba float64) {
cst := 0.005454154
if unittype == "metric" {
cst = 0.00007856
}
for i := range dia {
ba = ba + cst*dia[i]*dia[i]*wt[i]
}
return
}
func main() {
dia := []float64{8, 6, 8, 5, 4, 6, 7}
wt := []float64{10, 10, 10, 10, 10, 10, 10}
wt2 := []float64{25, 25, 25, 25, 25, 25, 25}
fmt.Println("basalarea imperial =", basalarea(dia, wt, "imperial"))
fmt.Println("basalarea metric =", basalarea(dia, wt2, "metric"))
}
</code></pre>
</div>
<a href="https://github.com/LarsenDR/forfuncGo/blob/master/basalarea.go">Go Code</a>
</p>
<p>
Note the Go file has a extra "txt" at the end to allow the files to be viewed in a web browser.
</p>
</td>
</tr>
</tbody>
</table>
</center>
<hr class="full" />
<div align="right">
<small>
<a rel="license" href="http://creativecommons.org/licenses/by-nc/3.0/us/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc/3.0/us/88x31.png" /></a><br />This <span xmlns:dc="http://purl.org/dc/elements/1.1/" href="http://purl.org/dc/dcmitype/Text" rel="dc:type">work</span> is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-nc/3.0/us/">Creative Commons Attribution-Noncommercial 3.0 United States License</a>.
<br/>
<br/>
Author: Dr. David R. Larsen, Copyright 2012<br/>
Created: October 9, 2012<br/>
Last Updated: August 21, 2017</small>
</div>
</td>
</tr>
</tbody>
</table>
</body>
</html>