Function to skip start of a signal

Dear SteveYrk,

SteveVrk said:

For calculating certain quantities, e.g. rms voltage, I would like to skip the first, say, 10m of a signal.

Surprisingly I did not find any function which does this (like "cut" or so). In frequency domain, dft supports skipping a time!

Perhaps I am totally misunderstanding your question Steve and I apologize for my lack of understanding if I am!

However, the dft() function innately allows for examining on a portion of the time domain waveform - and also implicitly provides a low-pass filter.

1. The dft() function syntax is:

dft(
o_waveform
n_from
n_to
x_num
[ t_windowName ]
[ n_param1 ]
[ n_adcSpan ]
)
=> o_waveform / nil

where n_from and n_to represent the initial and final time points respectively of your time domain waveform from which the DFT is computed. In the frequency domain, the low-pass filter the DFT implicitly provides is governed by the time span between n_from and n_to. Intuitively, any frequency domain component below this frequency will not be discernable in your time-domain sample as its period is greater than the time-domain sample.

Once again, it may be my misunderstanding, by it appears you need to set the value of n_from to 10ms in your case to examine only the portion after 10ms.

Shawn

Dear SteveYrk,

SteveVrk said:

For calculating certain quantities, e.g. rms voltage, I would like to skip the first, say, 10m of a signal.

Surprisingly I did not find any function which does this (like "cut" or so). In frequency domain, dft supports skipping a time!

Perhaps I am totally misunderstanding your question Steve and I apologize for my lack of understanding if I am!

However, the dft() function innately allows for examining on a portion of the time domain waveform - and also implicitly provides a low-pass filter.

1. The dft() function syntax is:

dft(
o_waveform
n_from
n_to
x_num
[ t_windowName ]
[ n_param1 ]
[ n_adcSpan ]
)
=> o_waveform / nil

where n_from and n_to represent the initial and final time points respectively of your time domain waveform from which the DFT is computed. In the frequency domain, the low-pass filter the DFT implicitly provides is governed by the time span between n_from and n_to. Intuitively, any frequency domain component below this frequency will not be discernable in your time-domain sample as its period is greater than the time-domain sample.

Once again, it may be my misunderstanding, by it appears you need to set the value of n_from to 10ms in your case to examine only the portion after 10ms.

Shawn

Hi Shawn, thanks for your response but yes, you are misunderstanding. I want a function that does the skipping in the time domain. I was saying I know that this works if I want to process data in frequency domain via dft function.

stddev(cutSignal(v("/vout") 10m 100m))

Thats what I want.

Use the clip function. This allows you to specify the range of the waveform you want.

Andrew