H(w,a,K) := abs(1 + a * exp(-%i*w*K));
load(draw);
draw2d( terminal=svg,dimensions=[748,367],
        grid=true,user_preamble="set mxtics; set mytics",
        xtics_axis=false,ytics_axis=false,ip_grid=[20,20],
        xtics={["0",0], ["{/Sympol p}",%pi],["2{/Symbol p}",2*%pi],["3{/Symbol p}",3*%pi],["4{/Symbol p}",4*%pi],
            ["5{/Symbol p}",5*%pi],["6{/Symbol p}",6*%pi],["7{/Symbol p}",7*%pi],["8{/Symbol p}",8*%pi],
            ["9{/Symbol p}",9*%pi],["10{/Symbol p}",10*%pi]},
        color=black,xlabel="{/Symbol w} (rad/s)",ylabel="{/=20 |}H ( e^{j{/Symbol w}}){/=20 |}",
        xaxis_type=solid,yaxis_type=solid,line_width=1.5,yrange=[0,2.5],
        axis_bottom=true,axis_top=false,axis_right=false,axis_left=true,
        key="{/Symbol a} = 1",color=blue,explicit((H(w,1,1)),w,0,10*%pi),
        key="{/Symbol a} = 0.75",color=red,explicit((H(w,0.75,1)),w,0,10*%pi),
        key="{/Symbol a} = 0.5",color=magenta,explicit((H(w,0.5,1)),w,0,10*%pi)
);