Error using optmize (line 9) Data length must be larger than 195 samples.

Hi, i try to optimize my Matlab code so i have written this code

 clc;

 clear all;

 close all;

 load('C:\Users\del.dell-PC\pfe\base de donnée\patient sans 
 crise\chb01_01_edfm.mat')

 deriv=val()/2.559375;

 Fs=256;

 t=(0:length(deriv)-1)/Fs;

 d=designfilt('lowpassfir','PassbandFrequency',0.45,'StopbandFrequency',0.5,'Passba
 ndRipple',3,'StopbandAttenuation',60,'DesignMethod','equiripple');

 a=filtfilt(d,deriv);

But i got this error message " Error using optmize (line 9) Data length must be larger than 195 samples." How could i fix this?