Basic Plot with Log scale of nonlinear function

I am new to matlab so my apologies for struggling with basics. I am plotting the following function:

y=(1.018*10^10)*[x/(1+((8.03*10^8)*x)^2) + (4*x/(1+4*((8.03*10^8)*x)^2))];

Based on the plot function I tried logspace but it gave me this error message:

??? Error using ==> mpower Inputs must be a scalar and a square matrix. To compute elementwise POWER, use POWER (.^) instead.

I tried setting a scale but was unsure how to properly write the log scale in terms of x:range 1:step size:range 2???

This plot is for a contrast agent used in MRI and this specifically is BPP theory. The end of the T1 and T2 plots are divergent while in another regime it is linear. I am trying to plot this on a scale from 10^-9 to 10^-5 and then another plot, preferably on the same plot the Relaxivities which are T1^-1 and T2^-1. For some reason when I plot this graph, the x scale is always -1 to 1.5 and the y-scale is 16.5 to 19??? Even more confusing because I have changed the scale of x but nothing else changes?

Thank you for the help. I was a Mathematica student trying to make the conversion.

Answer 1

[Honglei Chen]

You probably want to use ./, .*, and .^ instead.