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Re: [ferret_users] low pass filter

in The arguments first one is okay but the second argument will br the cut off frequency in your case it will be 1/120 (10 yr=120 months and you need to convert it to frequency domain) and the last argument is for weight..it is should be odd no..the more weight you give the smooth signal you get. Supoose you give 61 as a weight it will discard 30 data points from each end

There is another option in NCL i.e filwgts_lanczos function there you can do lowpass highpass and bandpass all just by altering 'ihp' value.

On Fri 10 Aug, 2018, 11:22 AM saurabh rathore, <rohitsrb2020@xxxxxxxxx> wrote:
Hello Sandeep

you should look into this thread for understanding.

regards, saurabh

On Fri, Aug 10, 2018 at 3:35 PM, Sandeep Mohapatra <sandeepmohapatra21@xxxxxxxxx> wrote:
I have gone through the low pass filter concept mentioned in ferret.

suppose i have monthly data of 696 months, 
i want to calculate 10 yr low pass filter.
And  I use the below fomula 

var1 = lsl_lowpass(var,696,121)

So, I just want to know whether this method is correct or not.

if not, please tell me the correct method.



Saurabh Rathore
Research Scholar (PhD.)
Centre For Oceans, Rivers, Atmosphere & Land Science Technology
Indian Institute Of Technology, Kharagpur
contact :- 91- 8345984434

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