Interpolating plot with isolines (2024)

Hi Jan,

I understand that you are trying to digitize and interpolate a plot with isolines to extract and plot constant angle lines on a 3D plot. You have collected some data points along these isolines, which include (x), (y), and (z) values, where (z) represents the angle value at each (x, y) location. Your goal is to interpolate these data points to fill in the gaps between the isolines, especially for angle values not directly measured.

Given the nature of your problem, it seems like you're facing challenges with griddata resulting in NaN values for extrapolated areas and issues with griddedInterpolant due to sample values errors. These problems often arise from how the data is prepared and fed into these functions or from attempting to extrapolate beyond the bounds of your data.

Here's a structured approach to tackle your problem using MATLAB:

1. Preparing Your Data

Ensure your data is in the correct format. Your data should be in three separate vectors of the same length, corresponding to (x), (y), and (z) values. For example:

2. Use griddata for Interpolation

Create a grid on which to interpolate your (z) values and use griddata for the interpolation. To address the issue of NaN values for extrapolated areas, you can limit your interpolation to the convex hull of your data points or use nearest neighbor interpolation to fill in NaN values.

3. Plotting the Interpolated Data

After interpolating the (z) values on your grid, you can plot the results to visualize the angle isolines in 3D.

Hope this helps.

Regards,

Nipun