Strange function fit to data points- sorting by first column vals?

Hi,

does anyone have any idea why my function has such a strange shape? In the modelling app I'm not getting this.

I think I need to sort the T values keeping the rows together maybe but is there a way to keep columns together and sort by the first column vals?

conductivity4=abs(set4(:,2));

scatter(set4(:,1),conductivity4)

T4=set4(:,1);

hold on

y=(1.236*10^(-12))*exp(0.01189.*T4)

plot(T4,y)

ylim([1 2.2]*10^(-11))

xlim([180 240])

Thanks!

Answer 1

[Voss]

I think it is the points not being in monotonic order in T4, and sorting them first will fix it, like you say.

% T4 values to use, in order:
T4_order = 180:240;

% create a random permutation of those values:
T4 = T4_order(randperm(numel(T4_order)));
% calculate the corresponding y values:
y=(1.236*10^(-12))*exp(0.01189.*T4);
% plot (should have the same problem as your plot):
figure();
plot(T4,y,'r');

% sort the T4:
T4 = sort(T4);
% calculate the corresponding y values:
y=(1.236*10^(-12))*exp(0.01189.*T4);
% plot (should be good):
figure();
plot(T4,y,'r');

[Em]

Thank you!

[Em]

This is great!

[Voss]

You're welcome!