Originally Posted by

**bceros** I知 trying to interpolate on a logarithmic scale for a program I知 working on and have been banging my head against the desk trying to develop a formula for this and I知 hoping maybe someone either already has one or can give me some assistance. The entire graph is situated in an arbitrary coordinate system (it痴 displayed on a screen, so the coordinate system is the x,y pixel coordinates.) So I know the screen coordinates of the two points and the real values of these points (what they user tells the program they are). Now I need to find the corresponding real value of a new point that is placed on the graph when I only know the screen coordinates.

Ex: The graph below, I would know the value of the red squares but do not know the value of the green square, but I know the "coordinates" of each. The X-axis is logarithmically scaled.

Further expanded example with numbers:

Say the left red square is at 100 pixels and represents a value of 1.

The right red square is at 500 pixels and represents 10.

The green square is at 200 pixels and I need to find it's value.