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In the world of computers,
time is generally mapped into integers too,
say .This is called ``discretizing'' or ``sampling.''
The highest possible frequency expressible on a
**mesh**
is
,which is the same as .Setting ,we see that the maximum frequency is
| |
(18) |

Time is commonly given in either seconds or sample units,
which are the same when .In applications, frequency is usually expressed in cycles per second,
which is the same as
**Hertz**,
abbreviated
**Hz**.
In computer work, frequency is usually specified in cycles per sample.
In theoretical work,
frequency is usually expressed in **radian**s
where
the relation between radians and cycles is .We use radians because, otherwise, equations are filled with 's.
When time is given in sample units,
the maximum frequency has a name:
it is the ``**Nyquist frequency**,''
which is radians or 1/2 cycle per sample.

** Next:** Fourier sum
** Up:** FOURIER SUMS
** Previous:** Superposition of sinusoids
Stanford Exploration Project

10/21/1998