Geografic-Information-System/scripts/r.mapcalc.simple/r.mapcalc.simple.html

<h2>DESCRIPTION</h2>

<em>r.mapcalc.simple</em> provides a wrapper to <em>r.mapcalc</em>.
Up to 6 maps can be combined using simple expressions.

<p>
The general syntax for the <b>expression</b> follows
<em><a href="r.mapcalc.html">r.mapcalc</a></em> expression format,
for example, <tt>A + B</tt> or <tt>exp(A + B)</tt> are valid.
The variables A, B, ..., F represent raster maps which are provided
as options <b>a</b>, <b>b</b>, ..., <b>f</b>.

<p>
The result name, i.e. the output raster map, is provided using the
option <b>output</b> and, unlike <em>r.mapcalc</em> it is not part
of the expression.

<p>
This module is meant for convenience (for users and programmers) while
the <em>r.mapcalc</em> module is a better choice for more complex
expressions and advanced usage.


<h2>NOTES</h2>

Differences to <em>r.mapcalc</em> module:

<ul>
    <li>The input raster map names and the output map raster name are
        separate from the expression (formula) which uses generic
        variable names (A, B, C, ...).
    <li>The output raster name is not included in the expression.
    <li>The expression is expected to be a single short one liner
        without the function <tt>eval()</tt>.
</ul>

Differences to <em>r.mapcalc.simple</em> module in GRASS GIS 5 and 6:

<ul>
    <li>The primary purpose is not being a GUI front end to
        <em>r.mapcalc</em>, but a wrapper which allows easy building of
        interfaces to <em>r.mapcalc</em> (including GUIs).
    <li>Whitespace (most notably spaces) are allowed
        (in the same way as for <em>r.mapcalc</em>).
    <li>The variable names are case-insensitive to allow the original
        uppercase as well as lowercase as in option names
        (unless the <b>-c</b> flag is used).
    <li>Option names for each map are just one letter (not amap, etc.).
    <li>Output option name is <b>output</b> as for other modules
        (not outfile).
    <li>Raster map names can be optionally quoted (the <b>-q</b> flag).
    <li>There is no expert mode
        (which was just running <em>r.mapcalc</em>).
    <li>The <b>expression</b> option is first, so it is possible to
        omit its name in the command line
        (just like with <em>r.mapcalc</em>).
    <li>Overwriting of outputs is done in the same way as with other
        modules, so there is no flag to not overwrite outputs.
</ul>


<h2>EXAMPLES</h2>


<h3>Basic examples</h3>

<div class="code"><pre>
r.mapcalc.simple expression="0" output=zeros
r.mapcalc.simple expression="1" output=ones
r.mapcalc.simple expression="2" output=twos
</pre></div>

<div class="code"><pre>
r.mapcalc.simple expression="A + B + C" a=zeros b=ones c=twos output=result1
</pre></div>

<div class="code"><pre>
r.mapcalc.simple expression="(A * B) / 2 + 3 * C" a=zeros b=ones c=twos output=result2
</pre></div>

<div align="center" style="margin: 10px">
<img src="r_mapcalc_simple.png" width="594px" height="495px"><br>
<i>Figure: r.mapcalc.simple graphical user interface</i>
</div>


<h3>Example expressions</h3>

Addition:

<div class="code"><pre>
A + B
</pre></div>

No spaces around operators are not recommended for readability,
but allowed in the expression:

<div class="code"><pre>
A+B
</pre></div>

More complex expression with a function:

<p>
<div class="code"><pre>
exp(A+C)+(B-2)*7
</pre></div>


<h2>SEE ALSO</h2>

<em>
<a href="r.mapcalc.html">r.mapcalc</a>,
<a href="r3.mapcalc.html">r3.mapcalc</a>,
<a href="t.rast.mapcalc.html">t.rast.mapcalc</a>,
<a href="g.region.html">g.region</a>
</em>


<h2>AUTHORS</h2>

Vaclav Petras, <a href="https://geospatial.ncsu.edu/geoforall/">NCSU GeoForAll Lab</a><br>
Michael Barton, Arizona State University (updated to GRASS 5.7)<br>
R. Brunzema (original 5.0 Bash version)

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