Hey there! Let’s work through this Excel exponential curve problem together. You’ve got a fixed k value of 0.25 and a fee range from 1% to 10%, but your previous formula attempts haven’t hit the expected curve shape—let’s break down reliable solutions and troubleshooting steps.

First, let’s assume your fee values are in column A (e.g., A2:A11, stored as decimal numbers like 0.01 for 1%, 0.02 for 2%, up to 0.10 for 10%). Excel’s EXP function relies on numeric inputs, so make sure you’re not using text-formatted percentages (if you have cells formatted as "1%", Excel stores them as 0.01 internally, but double-check with =A2*100 to confirm it returns 1).

1. Exponential Decay Curve (Value drops as fee increases) #

This is the go-to if higher fees lead to a diminishing outcome. Enter this in cell B2, then drag down to apply to your fee range:
=EXP(-0.25*A2)

• What it does: The negative coefficient (-0.25) creates a smooth decay curve. For 1% (0.01), it returns ~0.9975; for 10% (0.10), it gives ~0.9753.

2. Exponential Growth Curve (Value rises as fee increases) #

If higher fees correspond to a growing result, flip the sign of the k coefficient:
=EXP(0.25*A2)

• Example outputs: 1% gives ~1.0025, 10% gives ~1.0253.

3. Scaled Curve (Match specific starting/ending values) #

If you need the curve to anchor to a specific base value (e.g., 100 when fee=1%) and follow the exponential trend from there, adjust the formula with a scaling factor:

• For decay: =100*EXP(-0.25*(A2-0.01)) (sets value to 100 at 1%, decays exponentially after)
• For growth: =100*EXP(0.25*(A2-0.01)) (starts at 100 at 1%, grows exponentially)

Troubleshooting if Your Curve Still Doesn’t Match Expectations #

• Check coefficient application: Make sure you’re multiplying k directly by the fee value (not the percentage as a whole number—e.g., don’t use 1 instead of 0.01 for 1%).
• Visualize to validate: Select your fee and calculated value range, go to the Insert tab, and pick a Scatter with Smooth Lines chart. This lets you instantly compare the generated curve to your expected shape.
• Tweak scaling for target values: If you have a specific target (e.g., "when fee is 10%, value should be 50"), solve for the scaling factor algebraically. For decay: 50 = C*EXP(-0.25*0.10) → C = 50/EXP(-0.025) ≈ 51.26, so your formula becomes =51.26*EXP(-0.25*A2).

内容的提问来源于stack exchange，提问作者user7378789