How to plot the log scale?

If I have the following code:

syms t x ai di Kgr dc fc Rc fi_Ri Kei Kec fch_Rch_Nh0 fih_Rih_Nh0
g = @(t,x,ai,di,Kgr,dc,fc,Rc,fi_Ri,Kei,Kec,fch_Rch_Nh0,fih_Rih_Nh0)[Kgr*x(1)-dc*x(1)*x(2);ai*x(1)-di*x(2);fc*Rc*x(1)+fch_Rch_Nh0-Kec*x(3);fi_Ri*x(2)+fih_Rih_Nh0-Kei*x(4)]
ai=0.0474; di=0.1131; Kgr=5.78*10^(-3); dc=0.2*10^(-10); fc=0.1; Rc=4.5*10^(-5); fi_Ri=10.925*10^(-4); Kec=0.11; Kei=2.14;fch_Rch_Nh0=4.56*10^(1); fih_Rih_Nh0=7.16*10^(2) ;
   cutoff1=34.11*3150; cutoff2=3.8*3150; threshold1= 1.5*3150; threshold2= 1*3150;
[t,xa] = ode45(@(t,x) g(t,x,ai,di,Kgr,dc,fc,Rc,fi_Ri,Kei,Kec,fch_Rch_Nh0,fih_Rih_Nh0),[0 4000],[1 1 0 0]);
figure
plot(t,xa(:,3),'r')
   hline1=refline(0,cutoff1);
   hline2=refline(0,threshold1);
   set(hline1,'color','g','LineStyle','--')
   set(hline2,'color','g','LineStyle','-') 
hold on
plot(t,xa(:,4),'color','b')
   hline3=refline(0,cutoff2);
   hline4=refline(0,threshold2);
   set(hline3,'color','b','LineStyle','--')
   hline4.Color='m';
xlabel ('Time')
ylabel ('q_{PL}(t)')
title(['Tumor & Immune Biomarkers Shedding also by Healthy Cells'])

How can I plot t versus log x(3) and log x(4) instead of plot(t,xa(:,3))and plot(t,xa(:,4)) contained in the code? can I write plot(t,log (xa(:,3))) and plot((t,log (xa(:,4)))?

Thanks in advance.

Answer 1

[Star Strider]

‘can I write plot(t, log(xa(:,3))) and plot((t, log(xa(:,4)))?’

Yes, or you can use the semilogy plot:

semilogy(t, xa(:,3))
semilogy(t, xa(:,4))

[Esraa Abdelkhaleq]

Thanks a lot. But I tried the two methods and got different results!!

[Star Strider]

My pleasure.

The results appear to be different, because of the scaling on the y-axis. With your original code, the units will be in terms of ‘log(xa(:,c))’ (where ‘c’ is the column you choose). With semilogy, they will be in powers of 10.