You are getting the second plot, but only one data point of it, so it's being plotted as a point. However, since you do ot specify a marker style, you will not be able to see it.
If you want to see a single point, specify a markerstyle.
If you want to see a line, specify more than one y value by specifying all columns of fit_temp
plot(x,fit_temp(i,:),'b-')
