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Questions tagged [logistic-curve]

A common S-shaped ("sigmoid") curve, defined as $f(x) = L/(1+e^{-k(x-x_0)})$.

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Generate odds ratios across deciles / quantiles of an indpendent variable

With reference to the following figure from Bellomo et al., 2011: How exactly are the odds ratios across the deciles 'referenced against the 4th decile' calculated? My initial impression is that a ...
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How to calculate an index value between 1 and 0 for distance, based on a logistic function

I work with spatial ecology, and have calculated distances from one island to its neighboring islands. I want to transform these distances to index values between 0 and 1, where the closest islands ...
196 views

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Adjusting S-Curves (Sigmoid Functions) with Hyperparameters

I can define the sigmoid function in R with: ...
145 views

How to analyse growth rate in R?

Within the framework of an experiment I followed to growth rate of bird nestlings. I measured them every day for weight and tarsus. I have a number of continuous and categorical explanatory variables, ...
1k views

Fitting a dose response curve to 3 dose points

I have dose-response data sets, of 3 doses, 3 replicates for each dose. I'd like to fit a curve for these data sets and I'm mainly interested in the slope of the curve since I want to be able and ...
308 views

(How) Can I fit a dataset with some parameters fit globally?

I want to fit some sigmoidal curves that follow the following equation: bottom+(top-bottom)/(1+10**((logIC50-x)*HillSlope)) the parameters top and bottom should ...
400 views

Automatically finding starting values for a sigmoid curve

I have ~10.000 of vectors and I want to fit a sigmoid curve to each of them; in each case, I need to define starting parameters for fitting, so I want to find these parameters automatically. On ...
11k views

Looking for function to fit sigmoid-like curve

I'm looking for a function to fit sigmoid-like curves, from experimental data points. The model (the function) doesn't matter, it doesn't have to be physically relevant, I just want to be able to ...
2k views

Why is the logistic distribution called “logistic”?

What is "logistic" about the logistic distribution, in a common sense way? What is the etymology of and the lexical rationale for the name, not just pure math definition?
891 views

Fitting a logistic curve to cumulative data using glm()

I'm trying to fit a logistic curve to cumulative data, derived from satellite imagery. Previously, I have point observation data which were either 0s or 1s. Os being 'forest' and 1s being 'non-forest'....
174 views

Which steps have to be done before fitting logistic curve to time-series?

I want to cluster time-series concerning sales of products. In the database I have 26weeks after launching each products and units sold each week. One of the method of clustering is to cluster ...
63 views

Fitting Inspection Time Data to Curve

I have a set of Inspection Time data that consists of two variables: SOA (stimulus onset asynchrony) and Accuracy. This data refers to how accurately you can perform on a simple stimuli ...
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Estimating the slope of the straight portion of a sigmoid curve

I have been given this task and was stumped. A colleague asked me to estimate the $x_{upper}$ and $x_{lower}$ of the following chart: The curve is actually a cumulative distribution, and x is some ...