CMSIS - Interpolation on unequally spaced data

Looking at the documentation page, it seems the data for linear interpolation needs to be equally spaced (https://www.keil.com/pack/doc/CMSIS/DSP/html/arm_linear_interp_example_f32_8c-example.html#a5).
Is there any alternative for this in the library?

My data are peaks of ppg signal that can occur at any time within a predefined length window. I would need to interpolate them to a 4Hz grid for frequency analysis.