Plotting two different equations on the same graph/matlab -

while able plot fft( fast fourier transform) plot(x,y), unable plot fit line f(x) along fft. equations gathered curve fitting tool, took ten best fit , averaged come equation f(x).

what must f(x) plotted log(freq) , log(pow)

code:

row=69; col=69;  colormap gray whitebg('black')  iterations=10^3;   next=zeros(row,col); laplacian=zeros(row,col); critical=zeros(row,col);  b= zeros(row,col); lums=zeros(1000);   flw=0.5;  u=0.1;  crit=5; %bns=200; bns=1000;  k=1:iterations     b=b+(rand(row,col)-0.5);    next=b;  rns=5.; i=1:row j=1:col  rfromns=(col+rns-j);         critical(i,j)=0;         if i<=2 left=row; else left=(i-1);end         if i==row right=1; else right=(i+1);end         if (j<=2) top=1; else top=(j-1);end         if (j==col) bottom=j; else bottom=(j+1);end         l=b(i,top)+b(left,j)+b(right,j)+b(i,bottom)+0.5*(b(left,top)+b(right,top)+b(left,bottom)+b(right,bottom));         l=l-6.*b(i,j);         laplacian(i,j)=l;         bfromns=bns/rfromns^3;         if (abs(l)/((abs(b(i,j))+bfromns)+0.01))>crit; critical(i,j)=1; end         %if abs(l)>crit; critical(i,j)=1; end end end                j = 1:col             if (j==col) lum=0.;end             = 1:row              if (j>1) next(i,j)=(1-flw)*b(i,j)+flw*b(i,j-1); end;             if (j==1) next(i,j)=(1-flw)*b(i,j); end;              if (critical(i,j)==1)&& (j>1)   next(i,j)=b(i,j)*(1-flw-flw*u)+flw*b(i,j-1)+(flw*u)*b(i,j)/5.; end;             if i<2 left=row; else left=(i-1);end             if i==row right=1; else right=(i+1);end             if (j<=2) top=1; else top=(j-1);end             if (j==col) bottom=j; else bottom=(j+1);end              if (critical(left,j)==1) next(i,j)=next(i,j)+flw*u*b(left,j)/5.;end             if (critical(right,j)==1) next(i,j)=next(i,j)+flw*u*b(right,j)/5.;end             if (critical(i,top)==1) next(i,j)=next(i,j)+flw*u*b(i,top)/5.;end             if (critical(i,bottom)==1) next(i,j)=next(i,j)+flw*u*b(i,bottom)/5.;end              if (j==col) lum=lum+u*b(i,j)*b(i,j)+abs(laplacian(i,j)); end             end             end  lums(k)=lum;  b=next;                 %matplot(b) %if (k>00) surf(b); %plot(lums) %view([0 90]) %pause(0.001) %end end   c=fft(lums(129:iterations)); pow=abs(c).^2; pow=pow(2:(iterations-128)/2); freq=(2:(iterations-128)/2);  x=log(freq); y=log(pow);  %x=length(x);  x=0.6:.1:6.;  %linear model poly2 a1 = -0.155;   a2 = 0.2154;   a3 = 15.1; af(x) = a1*x.^2 + a2*x + a3;  %linear model poly3 b1 = 0.01805;   b2 = -0.3687;   b3 = 0.9874;   b4 = 14.29;  bf(x) = b1*x.^3 + b2*x.^2 + b3*x + b4;   %general model power2 c1 = -0.09124;   c2 = 2.179;   c3 = 15.34; cf(x) = c1*x.^c2+c3;   %general model rat02 d1 = 727.3;   d2 = -3.447;   d3 = 51.6;  df(x) = (d1) / (x.^2 + d2*x + d3);   %general model gauss1 e1 = 15.01;   e2 = 1.346;   e3 = 8.152;  ef(x) =  e1*exp(-((x-e2)/e3).^2);   %general model gauss2  w1 =  1.737;   w2 =  3.46; w3 =  2.333;   w4 =  30.03;   w5 =  -23.14; w6 =  28.23; wf(x) =  w1*exp(-((x-w2)/w3).^2) + w4*exp(-((x-w5)/w6).^2);    %general model sin1 g1 = 15.11;   g2 = 0.1526;   g3 = 1.428;   gf(x) =  g1*sin(g2*x+g3);    %linear model poly4 h1 =  0.0179;   h2 =  -0.252;   h3 =  1.047;   h4 =  -1.97;  h5 =  16.23;   hf(x) = h1*x.^4 + h2*x.^3 + h3*x.^2 + h4*x + h5;   %general model fourier1 m1 =  11.05;   m2 =  3.31;   m3 =  2.104;   m4 =  0.3644;   mf(x) =  m1 + m2*cos(x*m4) + m3*sin(x*m4);   %linear model p1 =  0.815; p2 =  0.1061; p3 =  8.904; pf(x) = p1*(sin(x-pi)) + p2*((x-10).^2) + p3;   f(x)=(af(x)+bf(x)+cf(x)+df(x)+ef(x)+wf(x)+gf(x)+hf(x)+mf(x)+pf(x))/10;    plot(x,y) plot(f(x)) 

matlab/octave therefore use hold keyword.

if want plot several things on 1 graph, start program hold on, execute 1 or more plot command, , finalize hold off.

example:

hold on; x = -10:0.1:10; plot (x, sin (x)); plot (x, cos (x)); hold off; 

documentation: https://www.gnu.org/software/octave/doc/interpreter/manipulation-of-plot-windows.html

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as documentation describes, plot call newplot command, removes previous plot result, hold on; such behavior prevented.