Programmer Guide/Command Reference/EVAL/window: Difference between revisions
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::*If ''x'' is a vector or matrix, the number of rows of ''x'' is used as window length and the result of '''window''' is a matrix with the same dimensions as ''x'' where each column contains the windowed values of the input column. | ::*If ''x'' is a vector or matrix, the number of rows of ''x'' is used as window length and the result of '''window''' is a matrix with the same dimensions as ''x'' where each column contains the windowed values of the input column. | ||
:::The window length must be greater than 2! | :::The window length must be greater than 2! | ||
:;<var>scale</var>: A boolean argument to enable/disable energy correction. If the energy correction is enabled (''scale''!=0), the window function is scaled by a factor that approximately equalises the energy loss caused by the windowing. | :;<var>scale</var>: A boolean argument to enable/disable energy correction. If the energy correction is enabled (''scale''!=0), the window function is scaled by a factor that approximately equalises the energy loss caused by the windowing. To preserve signal energy, ''scale'' should be set to 1, otherwise (to preserve signal amplitude) it should be 0. | ||
:;<var>lo</var>: lower boundary, must be a number | :;<var>lo</var>: lower boundary, must be a number | ||
:;<var>hi</var>: upper boundary, must be a number | :;<var>hi</var>: upper boundary, must be a number | ||
Revision as of 16:45, 6 April 2011
Compute a window function used for signal windowing in sighnal processing algorithms.
- Usage
window(type, x {, scale {, par}})- type
- selects the type of the window function (described below); must be number
- x
-
- If x is a scalar, the argument is used as window length and the result of window is a vector containing the window function.
- If x is a vector or matrix, the number of rows of x is used as window length and the result of window is a matrix with the same dimensions as x where each column contains the windowed values of the input column.
- The window length must be greater than 2!
- scale
- A boolean argument to enable/disable energy correction. If the energy correction is enabled (scale!=0), the window function is scaled by a factor that approximately equalises the energy loss caused by the windowing. To preserve signal energy, scale should be set to 1, otherwise (to preserve signal amplitude) it should be 0.
- lo
- lower boundary, must be a number
- hi
- upper boundary, must be a number
- Result
- The result r is a copy of x but the values of the elements of r are limited to the boundaries defined by lo and/or hi.
- ri,j is set to lo if xi,j is lower than lo (functions limit and limitlow)
- ri,j is set to hi if xi,j is greater than hi (functions limit and limithigh)
Example:
#a := eval vv(1,2,3,4,5,4,3,2,1)
#b := eval fill(9,0,1)
#c := eval limitlow($#a, 3)
// -> $#c = { 3 , 3 , 3 , 4 , 5 , 4 , 3 , 3 , 3 }
#d := eval limit($#b, 2, 6)
// -> $#d[*,0] = { 2 , 2 , 3 , 4 , 5 , 4 , 3 , 2 , 2 }
// $#d[*,1] = { 2 , 2 , 2 , 3 , 4 , 5 , 6 , 6 , 6 }
General window function
| Usage: | window(type, x, scale, par) |
| Parameters: | |
| type=0 -> none (square) | type=1 -> whanning |
| type=2 -> whamming | type=3 -> wblackman |
| type=4 -> wkaiser | type=5 -> wbartlett |
| type=6 -> wtaprect | type=7 -> wnuttall |
| type=8 -> wflattop | type=9 -> wgauss |
The arguments x, scale and par are the same as above.
arguments: x The window length (scalar, >2), the signal (vector or matrix, nrow(x)>2). If x is a matrix, every column is multiplied with the window. scale The scaling (0=unscaled, 1=scaled for rms(sig) ~ rms(sig * wnd) par optional window parameters
The result is the signal window of length x or the signal multiplied by the window.
