how to make the contour line more curvy

The contour line is straight, how to make it more curvy? I have uploaded the image i and raw data.

[DGM]

It's not clear how your data is arranged or whether this is even the same data or all that's required to plot it. There's only one 63x189 matrix in the file.

Neither 63 nor 189 are integer-divisible by 12, so it's hard to guess whether this needs to be reshaped. It doesn't look like it does. So how did you plot this? If there's other information needed, please include it.

[yuxuan]

sorry, i have uploaded the wrong data. Here's the correct data.

Answer 1

[VBBV]

xdata % your x data
ydata % your y data
zdata % your z data
v = min(min(zdata)):1:max(max(zdata))  % add finer step size for smoother /curvier lines 
contourf(xdata,ydata,zdata,v)  % use additional argument 

[DGM]

All that does is explicitly set the level list. That doesn't smooth or interpolate anything.

[xdata ydata zdata] = peaks(10); % low-resolution data

v = min(min(zdata)):1:max(max(zdata));  % add finer step size for smoother /curvier lines 
contourf(xdata,ydata,zdata,v)  % use additional argument 

% double the number of levels
v = min(min(zdata)):0.5:max(max(zdata));  % add finer step size for smoother /curvier lines 
contourf(xdata,ydata,zdata,v)  % use additional argument 

The level curves are just as jagged. There's just more of them.

[VBBV]

From the figure attachment the data looked like it's sufficiently smoothed, but was plotted at a coarse step. Yes, if the data is coarsely spaced that option doesn't smooth as you told.

@yuxuan , you can try this function to make the lines more curvy given in this link.

https://www.mathworks.com/help/matlab/ref/smoothdata.html

[Mathieu NOE]

have a look at

Smooth noisy data in two dimensions - MATLAB smoothdata2 - MathWorks France

or there are alternatives on the Fex , like :

smooth2a - File Exchange - MATLAB Central (mathworks.com)

smoothn - File Exchange - MATLAB Central (mathworks.com)

Contour Line Smoothing - File Exchange - MATLAB Central (mathworks.com)