The paper presents formulas for calculating the parameters of exponential and logarithmic basic functions for the interpolation of the increasing function set by the table. Cases with even and odd numbers of argument steps are considered. The main goal was to prevent interpolation convexity, so the joining of derivatives was relegated to minor positions. It has been suggested that jumps in a derivative should be regarded as quality factors for basic data when visual examination is performed. The test case involved comparing two variants of pasting basic functions and discussing the issue of form-keeping. An example of processing experimental calibration data is demonstrated. The procedure is presented in the Pascal language.