How to remove negative values using tanh and have higher y-axis values?

I am new to Matlab and want to make a response time signal for our project using Matlab code like the same one on the image but with a filtered and smoother one. I have trouble making the y-axis the same as the image. Can you help me with my problem? Thank you.

x = linspace (117, 117.8);

e1 = tanh(117.3*(x-117.35)) + randn(size(x))/8;

plot(x,e1)

%xlim ([117 117.8]); ylim ([1900 1950]);

xlabel("Time (s)")

ylabel("Resistance (Ω)")

Answer 1

[Image Analyst]

Try movmedian

x = linspace (117, 117.8, 1000);
e1 = tanh(117.3*(x-117.35)) + randn(size(x))/8;
plot(x,e1)
%xlim ([117 117.8]); ylim ([1900 1950]);
xlabel("Time (s)")
ylabel("Resistance (Ω)")
ySmooth = movmedian(e1, 31);
hold on
plot(x, ySmooth, 'r-', 'LineWidth', 2)
grid on;
xlabel('x');
ylabel('e1')
legend('e1', 'e1 smoothed', 'Location', 'northwest')

The median filter reduces noise while keeping true steps intact ans sharp (steep).

Change the window size to have more or less smoothing.

[Stella]

Thank you!!! I saw what was lacking in my previous code. Is it also possible to have higher values for the y-axis using the same code? Because my advisor wants it to have like 1900 resistance and not negative, and that part is where I am struggling with. Sorry, I am just new to Matlab.

[VBBV]

e1 = 1935+tanh(117.3*(x-117.35)) + randn(size(x))/8;

Since baseline value is around 1935, add that constant as above

[Stella]

Thank you for the answers and explanations!! Have a nice day!

[Image Analyst]

You can use ylim to set the lower and upper limit for the y axis. For example to have it display only in a viewport from 0 to 2:

ylim([0, 2]);

Answer 2

[Sulaymon Eshkabilov]

Here is the corrected solution.

x = linspace (117, 117.8);
e1 = tanh(117.3*(x-117.35)) + randn(size(x))/8;
plot(x,e1*1e3)  % Note that it was magnified by 1000 and thus, unit become mOhm
xlabel("Time (s)")
ylabel("Resistance (mΩ)")   % Because of *1000 scaling factor
E1 = round(e1);             % To display nice looking integer numbers 
yticks(min(E1)*1e3-200:200:max(E1)*1e3+400), grid on

[Stella]

Thank you!!! I am also confused if i can only make positive values for the resistance axis?