fir1 — Design windowed-sinc FIR filters.

fir1(n, Wn) designs an order-n FIR filter using a Hamming-windowed sinc response. Scalar Wn creates a low-pass filter by default; a two-element Wn creates a band-pass filter by default. Add a filter type string for high-pass or stop-band designs.

Syntax

fir1(n, Wn)

How fir1 works

• Returns a row vector with n + 1 coefficients.
• Wn uses MATLAB's normalized digital convention where 1 is Nyquist.
• Supported filter types are low, high, bandpass, and stop.
• A custom window vector of length n + 1 may be supplied.
• Filters are scaled by default; pass noscale to skip passband normalization.

Does RunMat run fir1 on the GPU?

Host-side coefficient design only.

The resulting coefficient vector can be passed to filter or filtfilt with gpuArray signal data.

Examples

Design a low-pass FIR filter

b = fir1(4, 0.5);
fprintf('%d %.4f\n', length(b), sum(b));

Expected output:

5 1.0000

Design coefficients for a FIR low-pass response plot

fs = 1000;
fc = 100;
N = 51;
wn = fc / (fs/2);
b = fir1(N-1, wn, 'low');
[H, w] = freqz(b, 1, 512, fs);
fprintf('%d %.1f %.1f\n', length(b), w(1), w(end));

Expected output:

51 0.0 499.0

Use a custom rectangular window without scaling

w = ones(1, 11);
b = fir1(10, 0.3, w, 'noscale');

Using fir1 with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how fir1 changes the result.

FAQ

Related Math functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how fir1 is executed, line by line, in Rust.

• View the source for fir1 in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.

• RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
• Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.

Getting started · Benchmarks · Pricing