Curve-fit with zero offset
Say you are measuring some signal, which you expect to show an exponential decay, but you are unsure of the zero-point on your measuring device. If you want to measure the time constant of the decay you need to know what it’s decaying to. For a signal s,
In order to do conventional least-squares fitting to 
Step response of NIH 3T3 fibroblasts to ionomycin
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