One of the types of objects in Praat. A Matrix object represents a function z (x, y) on the domain [xmin, xmax] × [ymin, ymax]. The domain has been sampled in the x and y directions with constant sampling intervals (dx and dy) along each direction. The samples are thus z [iy] [ix], ix = 1 ... nx, iy = 1 ... ny. The samples represent the function values z (x1 + (ix - 1) dx, y1 + (iy - 1) dy).
Matrix commands
Creation:
-
• Create Matrix...
-
• Create simple Matrix...
-
• Read from file...
-
• Read Matrix from raw text file...
-
• Read Matrix from LVS AP file...
Drawing:
-
• Matrix: Draw rows...
-
• Matrix: Draw contours...
-
• Matrix: Paint contours...
-
• Matrix: Paint cells...
-
• Matrix: Scatter plot...
-
• Matrix: Draw as squares...
-
• Matrix: Draw value distribution...
-
• Matrix: Paint surface...
Modification:
-
• Matrix: Formula...
-
• Matrix: Scale...
Inside a Matrix object
With Inspect, you will see the following attributes.
-
xmin, xmax ≥ xmin
-
x domain.
-
nx ≥ 1
-
number of columns.
-
dx > 0.0
-
distance between columns.
-
x1
-
x value associated with first column.
-
ymin, ymax ≥ ymin
-
y domain.
-
ny ≥ 1
-
number of rows.
-
dy > 0.0
-
distance between rows.
-
y1
-
y value associated with first row.
-
z [1..ny] [1..nx]
-
The sample values.
After creation of the Matrix, xmin, xmax, ymin, ymax, nx, ny, dx, dy, x1, and y1 do not usually change. The contents of z do.
Normally, you will want xmin ≤ x1 and xmax ≥ x1 + (nx - 1) dx.
Example: simple matrix
If a simple matrix has x equal to column number and y equal to row number, it has the following attributes:
-
xmin = 1; xmax = nx; dx = 1; x1 = 1;
-
ymin = 1; ymax = ny; dy = 1; y1 = 1;
Example: sampled signal
If the matrix represents a sampled signal of 1 second duration with a sampling frequency of 10 kHz, it has the following attributes:
-
xmin = 0.0; xmax = 1.0; nx = 10000 ; dx = 1.0·10-4; x1 = 0.5·10-4;
-
ymin = 1; ymax = 1; ny = 1; dy = 1; y1 = 1;
Example: complex signal
If the matrix represents a complex spectrum derived with an FFT from the sound of example 2, it has the following attributes:
-
xmin = 0.0; xmax = 5000.0; nx = 8193 ; dx = 5000.0 / 8192; x1 = 0.0;
-
ny = 2 (real and imaginary part);
-
ymin = 1 (first row, real part);
-
ymax = 2 (second row, imaginary part);
-
dy = 1; y1 = 1; (so that y is equal to row number)
Links to this page
© ppgb 20030216