Biomedical Engineering Reference
In-Depth Information
the same as Example 2.4.6 except that the sine has
been replaced by a cosine.
the correct orientation.) Also construct and plot
the ensemble standard deviation.
12. Demonstrate that 1-Hz and 4-Hz cosine waves are
orthogonal by multiplying them together and
averaging the product. (Note when you multiply
be sure to use the point-by-point multiplication,
'.*'.)
13. The file two_var.mat contains two variables x
and y. Are either of these variables random? Are
they orthogonal to each other?
14. The file nerve.mat contains two signals, x and y,
along with a time vector, t. The two signals
represent nerve action potentials taken
simultaneously at two different sections of
a nerve axon along with inevitable noise. Use
cross-correlation to determine the average time
delay between the two signals. Assume the
sampling frequency of the nerve signals was
2 kHz.
15. Develop a program along the lines of Example
2.4.10 to determine the correlation in heart rate
variability during meditation. Load file
Hr_med.mat, which contains the heart rate
(beats/min as a function of time) in variable
hr_med and the time in variable t_med, then
determine and plot the autocovariance. The result
will show that the heart rate under meditative
conditions contains some periodic elements. Can
you determine the frequency of these periodic
elements?
MATLAB problems
11. Load the data in ensemble_data.mat found on
the CD. This file contains a data matrix labeled
''data.'' The data matrix contains 100 responses of
a signal in noise. Determine whether the responses
are stored in the rows or columns of the matrix.
Plot several randomly selected samples of these
responses. Is it possible to identify the signal from
any single record? Construct and plot the ensemble
average for these data. (Be sure that the matrix is in
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