math::filters(3tcl)

✨ NAME ✨

okay so bestie, math::filters is the Digital filters page from the Tcl Math Library 💖 it lives in the 3tcl manual, and it's all about filtering your data, no cap.

---

🦋 SYNOPSIS 🦋

package require Tcl 8.6 9

package require TclOO

package require math::filters ?0.3?

::math::filters::filterButterworth lowpass order samplefreq cutofffreq

::math::filters::filter coeffs data

::math::filters::filterObj new coeffs yinit

$filterObj filter x

$filterObj reset

like yes, it needs Tcl 8.6 or 9 and it needs TclOO too, because we're object-oriented in this house 💅

---

🌸 DESCRIPTION 🌸

The math::filters package implements digital filters, notably Butterworth low-pass and high-pass filters. The procedures let you filter an entire data series or filter data one by one. Both. Your choice. Main character energy either way ✨

---

🎀 PROCEDURES 🎀

The package defines the following public procedures:

• ::math::filters::filterButterworth lowpass order samplefreq cutofffreq — figure out the coefficients for a Butterworth filter of the given order. You get back a list of the x-coefficients, the y-coefficients, and the scale. Here's the formula, where n is the filter order:

                                 n             n
                  scale * y_k = sum x_(k-i) + sum y_(k-i)
                                i=0           i=1

• bool lowpass — generate a low-pass filter (1) or a high-pass filter (0) 👑
• integer lowpass — the order of the filter to be generated
• double samplefreq — sampling frequency of the data series
• double cutofffreq — cut-off frequency for the filter

bestie the second one says lowpass in the original, not order, and I'm not about to gaslight you by "fixing" it. Transcribing it fr fr 🫶

• ::math::filters::filter coeffs data — filter the entire data series based on the filter coefficients. whole series, one call, slay.
  • list coeffs — list of coefficients as generated by filterButterworth (or in fact any similar list of coefficients)
  • list data — data to be filtered
• ::math::filters::filterObj new coeffs yinit — create a filter object. The initial x data are taken as zero. The initial y data can be prescribed. If they're not given, they're taken as zero as well.
  • list coeffs — list of coefficients as generated by filterButterworth (or in fact any similar list of coefficients)
  • list yinit — (Optional) initial data for the filter result.
• $filterObj filter x — filter a single value and return the result.
  • double x — the value to be filtered
• $filterObj reset — reset the filter object (start anew) 🔄

---

💜 KEYWORDS 💜

digital, filtering

---

🌈 CATEGORY 🌈

Mathematics

---

🍓 COPYRIGHT 🍓

Copyright (c) 2020 by Arjen Markus

---

and that's the whole vibe check 💖 this is tcllib, version 0.3, and the page itself is math::filters(3tcl) — go filter something gorgeous, bestie 💅✨🦋