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# scipy.signal.sweep_poly

`scipy.signal.``sweep_poly`(t, poly, phi=0)

  Frequency-swept cosine generator, with a time-dependent frequency specified as a polynomial.

  This function generates a sinusoidal function whose instantaneous frequency varies with time. The frequency at time t is given by the polynomial poly.

  Parameters : | t : ndarray Times at which to evaluate the waveform. poly : 1D ndarray (or array-like), or instance of numpy.poly1d The desired frequency expressed as a polynomial. If poly is a list or ndarray of length n, then the elements of poly are the coefficients of the polynomial, and the instantaneous frequency is `f(t) = poly[0]*t**(n-1) + poly[1]*t**(n-2) + ... + poly[n-1]` If poly is an instance of numpy.poly1d, then the instantaneous frequency is `f(t) = poly(t)` phi : float, optional Phase offset, in degrees. Default is 0.
  Returns : | A numpy array containing the signal evaluated at ‘t’ with the requested : time-varying frequency. More precisely, the function returns : `cos(phase + (pi/180)*phi)` where `phase` is the integral (from 0 to t) of ``2 * pi * f(t)``; : ``f(t)`` is defined above. :

  See also

  `scipy.signal.waveforms.chirp`

  Notes

  New in version 0.8.0.

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