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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<TITLE>FORMAT Control the Format of Matrix Display
</TITLE>
</HEAD>
<BODY>
<H2>FORMAT Control the Format of Matrix Display
</H2>
<P>
Section: <A HREF=sec_io.html> Input/Ouput Functions </A>
<H3>Usage</H3>
FreeMat supports several modes for displaying matrices (either through the
<code>disp</code> function or simply by entering expressions on the command line.
There are several options for the format command. The default mode is equivalent
to
<PRE>
format short
</PRE>
<P>
which generally displays matrices with 4 decimals, and scales matrices if the entries
have magnitudes larger than roughly <code>1e2</code> or smaller than <code>1e-2</code>. For more
information you can use
<PRE>
format long
</PRE>
<P>
which displays roughly 7 decimals for <code>float</code> and <code>complex</code> arrays, and 14 decimals
for <code>double</code> and <code>dcomplex</code>. You can also use
<PRE>
format short e
</PRE>
<P>
to get exponential format with 4 decimals. Matrices are not scaled for exponential
formats. Similarly, you can use
<PRE>
format long e
</PRE>
<P>
which displays the same decimals as <code>format long</code>, but in exponential format.
You can also use the <code>format</code> command to retrieve the current format:
<PRE>
s = format
</PRE>
<P>
where <code>s</code> is a string describing the current format.
<H3>Example</H3>
We start with the short format, and two matrices, one of double precision, and the
other of single precision.
<PRE>
--> format short
--> a = randn(4)
a =
1.9819 -2.4403 0.3082 -0.8708
0.3885 0.6777 -2.1203 -0.6899
-0.8923 -1.0126 -1.1448 -0.3336
-0.5528 -0.2117 -0.6066 0.1530
--> b = float(randn(4))
b =
1.6282 -0.9987 -0.0002 0.7346
-0.1461 -0.4450 0.3260 0.0591
-0.1927 -0.2583 -0.3209 -1.7827
-0.4694 -0.2961 -0.3487 -0.1476
</PRE>
<P>
Note that in the short format, these two matrices are displayed with the same format.
In <code>long</code> format, however, they display differently
<PRE>
--> format long
--> a
ans =
1.98194242245660 -2.44033999910309 0.30822105452542 -0.87083520854217
0.38848412098646 0.67772654122050 -2.12029702950896 -0.68985792035578
-0.89231827506021 -1.01256221976480 -1.14477420632547 -0.33359041318909
-0.55283586680694 -0.21170713821002 -0.60660544623052 0.15300924745427
--> b
ans =
1.6282195 -0.9986902 -0.0002282 0.7346091
-0.1460750 -0.4449911 0.3259999 0.0591399
-0.1926918 -0.2583237 -0.3208777 -1.7827009
-0.4693597 -0.2961315 -0.3487136 -0.1476461
</PRE>
<P>
Note also that we we scale the contents of the matrices, FreeMat rescales the entries
with a scale premultiplier.
<PRE>
--> format short
--> a*1e4
ans =
1.0e+04 *
1.9819 -2.4403 0.3082 -0.8708
0.3885 0.6777 -2.1203 -0.6899
-0.8923 -1.0126 -1.1448 -0.3336
-0.5528 -0.2117 -0.6066 0.1530
--> a*1e-4
ans =
1.0e-04 *
1.9819 -2.4403 0.3082 -0.8708
0.3885 0.6777 -2.1203 -0.6899
-0.8923 -1.0126 -1.1448 -0.3336
-0.5528 -0.2117 -0.6066 0.1530
--> b*1e4
ans =
1.0e+04 *
1.6282 -0.9987 -0.0002 0.7346
-0.1461 -0.4450 0.3260 0.0591
-0.1927 -0.2583 -0.3209 -1.7827
-0.4694 -0.2961 -0.3487 -0.1476
--> b*1e-4
ans =
1.0e-04 *
1.6282 -0.9987 -0.0002 0.7346
-0.1461 -0.4450 0.3260 0.0591
-0.1927 -0.2583 -0.3209 -1.7827
-0.4694 -0.2961 -0.3487 -0.1476
</PRE>
<P>
Next, we use the exponential formats:
<PRE>
--> format short e
--> a*1e4
ans =
1.9819e+04 -2.4403e+04 3.0822e+03 -8.7084e+03
3.8848e+03 6.7773e+03 -2.1203e+04 -6.8986e+03
-8.9232e+03 -1.0126e+04 -1.1448e+04 -3.3359e+03
-5.5284e+03 -2.1171e+03 -6.0661e+03 1.5301e+03
--> a*1e-4
ans =
1.9819e-04 -2.4403e-04 3.0822e-05 -8.7084e-05
3.8848e-05 6.7773e-05 -2.1203e-04 -6.8986e-05
-8.9232e-05 -1.0126e-04 -1.1448e-04 -3.3359e-05
-5.5284e-05 -2.1171e-05 -6.0661e-05 1.5301e-05
--> b*1e4
ans =
1.6282e+04 -9.9869e+03 -2.2825e+00 7.3461e+03
-1.4608e+03 -4.4499e+03 3.2600e+03 5.9140e+02
-1.9269e+03 -2.5832e+03 -3.2088e+03 -1.7827e+04
-4.6936e+03 -2.9613e+03 -3.4871e+03 -1.4765e+03
--> b*1e-4
ans =
1.6282e-04 -9.9869e-05 -2.2825e-08 7.3461e-05
-1.4608e-05 -4.4499e-05 3.2600e-05 5.9140e-06
-1.9269e-05 -2.5832e-05 -3.2088e-05 -1.7827e-04
-4.6936e-05 -2.9613e-05 -3.4871e-05 -1.4765e-05
</PRE>
<P>
Finally, if we assign the <code>format</code> function to a variable, we can retrieve the
current format:
<PRE>
--> format short
--> t = format
t =
short
</PRE>
<P>
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</HTML>
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