Curve Fitting for multiple plots in single graphs

plot(XCS1,VYS1,'>','MarkerIndices',1:1:100,"LineWidth",2,"Color","Red","MarkerFaceColor","white");
hold on;
plot(XCS2,VYS2,'s','MarkerIndices',1:1:100,"LineWidth",2,"MarkerFaceColor","white");
hold on;

Unrecognized function or variable 'XCS1'.

As a part of code shown above i have to exract data from various files and plot it on one graph. Now this graph has multiple data points correspoing to x and y corrdinates. I want to do curvefitting over all the data point. How do proceed with it.

cftool allows me to fit curve for the single x and y values but i have multiple x's and y's coming from different files.

And after plotting basic curve fitting allows only over single data set i.e. fitting curve for D9 or D10 and not as entire plot.

I have attached image of graph below. for reference.

What i would like to have my graphs look like is shown below the Black line shows the fitted curve.

Answer 1

[Matt J]

Just concatenate the x,y, data.

x=[XCS1(:);XSC2(:)];
y=[VYS1(:);VYS2(:)];

cfit = fit(x,y,fitType)

[Yashvardhan Bhati]

Thanks @Matt J. Solution provided works well.