This example shows how to design a minimum-order lowpass FIR filter with a passband frequency of 0.37*pi rad/sample, a stopband frequency of 0.43*pi rad/sample (hence the transition width equals 0.06*pi rad/sample), a passband ripple of 1 dB and a stopband attenuation of 30 dB.
Fpass = 0.37;
Fstop = 0.43;
Ap = 1;
Ast = 30;
Refer the article below for more details on designing FIR and IIR filters based on frequency response specifications using the designfilt function in the Signal Processing Toolbox® product.