Questions tagged [curves]

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16
votes
5answers
29k views

Similarity measures between curves?

I would like to compute the measure of similarity between two ordered sets of points---the ones under User compared with the ones under Teacher: The points are curves in 3D space, but I was thinking ...
14
votes
2answers
1k views

Checking for a statistically significant peak

I have a set of data, $y$ and $x$. I would like to test the following hypothesis: There is a peak in $y$; that is as $x$ increases, $y$ first increases and then decreases. My first idea was fitting $...
11
votes
1answer
10k views

How to form a Precision-Recall curve when I only have one value for P-R?

I have a data mining assignment where I make a content-based image retrieval system. I have 20 images of 5 animals. So in total 100 images. My system returns the 10 most relevant images to an input ...
8
votes
1answer
2k views

Shape detection for time series data

I have a large collection of time series - measurements taken every 15 minutes (96 measurements in a day) over the span of 1 year at various different locations. I've broken up each time series into ...
7
votes
2answers
6k views

Fit between two curves

I am trying to determine the fit between two curves (example shown below). Both curves are plotted here as a bunch of XY data points (not functions). The curves represent the trajectories of two ...
7
votes
1answer
52 views

Does it take progressively fewer EXTRA correct answers to move up a grading curve in standardised exams?

A previous year's grading curve for an exam I will be sitting is : Assuming the exam has 100 (or any number of) questions each equally weighted, will it take fewer extra correct answers to move up ...
7
votes
0answers
544 views

Fitting the differences between two curves [closed]

The problem I'm trying to solve is to algorithmically figure out whether two curves converge or diverge in a graph (visually the problem is almost trivial). For examples: The left one is convergence, ...
5
votes
1answer
932 views

The issue of quantile curves crossing each other

While trying to perform some quantile regressions on some data I have encountered a classic problem: the 0.25,0.50, 0.75, 0.95 quantile curves are crossing each other (I am dealing with linear curves)....
5
votes
1answer
312 views

Getting ROC curve from markov chain in r

I've been working on some attribution modeling in R, following the markov chain-based methodology described here. In order to compare the sensitivity and specificity trade-offs of using models of ...
4
votes
1answer
125 views

ROC curve: small focused sample vs large sample

Background I'm currently reading the book Data ming: practical machine learning tools and techniques and came across the following ROC curve: The text corresponding to this figure: Method A ...
4
votes
1answer
635 views

How can Precision-Recall (PR) curves be used to judge overall classifier performance when Precision and Recall are class based metrics?

How can Precision-Recall (PR) curves be used to judge overall classifier performance when Precision and Recall are class based metrics? Since in a binary classifier, there are two classes, often ...
4
votes
1answer
55 views

How do I detect the “corner” in a set of data as it arrives?

Apologies from the start if my terminology is inaccurate, but what I have is a series of measurements that are made over a short time period from a hardware device to which I have just supplied a ...
4
votes
0answers
8k views

Test for statistical difference between two curves on same plot?

I've got data plotted for A/Ci curves (plant physiology, A=photosynthesis rate, Ci=internal CO2 concentration--essentially it's a dose-response relationship). Generally, when this type of data is ...
3
votes
3answers
9k views

In statistical terminology, what is the opposite of “peak”?

When we see a curve (or a normal distribution), we describe the highest value as "peak". Let's imagine we have a curve with only a minimum value (like an inverted hat), what do we call that minimum ...
3
votes
2answers
739 views

Average curve from set of curves

I have done some initial analyses on some patient datasets regarding neuro-degenerative diseases. A method I've used is DFA (Detrended Fluctuation Analysis) in MATLAB, which produced a family of ...
3
votes
0answers
185 views

Comparing two (or more) curves

I'm rather new to R and statistics. I'm analyzing intonation curves (time, fundamental frequency), and I'm interested in comparing pitch curves of different speakers. I am particularly interested in ...
3
votes
0answers
1k views

Statistical comparison between two curves

I have two time course experiments of the same study, and I want to determine if the time course curve is statistically significant or not. Let's say I treated a group of people with drug A, measure ...
2
votes
1answer
1k views

Curvilinear relationship with moderator

I am trying to moderate a curve and determine which equation I should follow. A simple curvilinear relationship has the following equation: (1) $Y = b_0 + b_1X + b_2X^2$ (i.e. a linear term and a ...
2
votes
1answer
89 views

Gaussian Process for Closed Curves

A Gaussian process gives a probability distribution over functions that pass through the data points. Is there a way to parameterize the Gaussian process to give a probability distribution over closed ...
2
votes
1answer
9k views

Tutorials for drawing an ROC curve

Are there tutorials you recommend that teach how to draw an ROC curve? Thanks.
2
votes
2answers
111 views

Estimation and comparison of flowering curves

I am a research scholar and monitoring phenological events of timber line at Himalayan region from past 4 years. During data analysis I found a research paper Estimation and comparison of flowering ...
2
votes
1answer
244 views

Choosing estimator based on Precision-Recall Curve

I hope you will help with this one. Below you see my Precision-Recall curves after performing 10-fold Stratified Cross Validation on my dataset. Note that my dataset is imbalanced that's why I'm ...
2
votes
3answers
206 views

Are there methods for automatically detecting features of a curve?

I have a raw discrete data(curves). I need to find methods for detecting features of each curve. Some example features: 1) Stable growing 2) Fast growing 3) Stable falling 4) Fast falling 5) And so ...
2
votes
2answers
2k views

Convex vs. concave curve - measurement or index

I am interested in a measurement or index that will tell me if a curve is more convex or concave versus a straight line. This curve is sampled in n points and I know the x and y coordinates of these ...
2
votes
0answers
29 views

how to calculate curvature of multivariate function?

EDIT1: tried to clarify the question Context In the context of an MCMC investigation of non-linear interaction effects in dichotomous models, I am creating data generating processes based on the ...
2
votes
0answers
149 views

Comparing two curves with peaks

I have a question about analysis method and I would be very grateful for the help! So, I have two groups: Active and Placebo, each group is measured for 20 different concentrations (from 1 to 20) 6 ...
2
votes
0answers
367 views

Comparing facial curvature of two human faces

I need help determining if what I'm doing is sufficient. I have extracted the "curvature" from two human faces (essentially the curve that goes from one ear, down the face to the chin, and back up to ...
2
votes
0answers
68 views

Hilbert curves: bounds / probabilities of preserving neighbors

Hilbert Curves (Wikipedia) are space-filling curves said to "fairly well preserve locality". Do you know any theoretical results here, such as bounds that neighbors within a radius of $\varepsilon$ ...
1
vote
1answer
87 views

Road condition: Project future condition by appending part of a deterioration curve?

I inspect a road network's condition every three years: ...
1
vote
1answer
679 views

find a general formula between two parameters using curve-fit

I am trying to study the relationship between two parameters say A and B for an image. For a single scene S1, I take 20 images ...
1
vote
1answer
62 views

What method can I use to produce a single curve from a number of curves?

I am looking for a good method to combine a set of curves into a single curve. Those curves have been produced by performing a measurement/testing n-number of times under similar conditions. What I ...
1
vote
1answer
641 views

“Changing” standard deviation?

I will admit to being just a hair about a novice when it comes to stats, but I feel like I have a decent working knowledge of things such as normal distribution, linear curves, standard deviations, ...
1
vote
1answer
189 views

Curve disaggregation with neural network

I have to extract a specific curve from an aggregate curve. An example is illustrated in the picture below, the blue curve is the aggregate curve, and I want to extract the red curve from the latter. ...
1
vote
1answer
737 views

How to determine signficant difference between 2 curves?

I have data on age, gender and weights of children. For example: ...
1
vote
0answers
24 views

How to represent local significant differences between curves

I want to compare some curves to a 'normality corridor', and I would like to show in what regions (x values) the difference is significant.Take the example below, where I want to compare the dashed ...
1
vote
1answer
308 views

ROC curve:difference between FPR x TPR and false positives x true positives

Background I'm trying to understand ROC curves, however I sometimes read that you can simply go one up for a True positive (TP) and one to the right for a False positive (FP), as mentioned here: ...
1
vote
1answer
88 views

Clustering curves

I am trying to cluster gas wells based on their production behavior based on Gas/Water ratio vs cumulative water produced plots. Would appreciate suggestions to solve this problem.
1
vote
0answers
25 views

Constant Curve for Cumulative Binomial

I am simulating traffic flow and have come across a rather interesting statistics problem that I'm having trouble wrapping my head around. I am modeling a stretch of road comprised of 2 lanes. Lets ...
1
vote
0answers
129 views

Statistical test to use to compare EMG waveforms with only the mean and sd?

I have to compare processed EMG waveforms (smooth curves) that I recorded from 7 different leg muscles of 4 different subjects to reference EMG data (Winter book). The problem is that for the ...
1
vote
0answers
74 views

Measuring magnitude of variation between 2 one-phase association exponential curves

I am currently testing the independence of two unpaired conditions A and B; with each condition representing a set of 12 values (aka bins) that compose a one-phase association exponential curve. Each ...
1
vote
0answers
206 views

Types of growth curves that can be compared using statmod compareGrowthCurves

I'm using the function compareGrowthCurves in the R package statmod, but I can't seem to find an explanation of what types of curve this is valid for. Does anyone ...
1
vote
0answers
434 views

Integrate first derivation - area under curve of first derivation

I want to calculate the area under the first derivate. Can I do that with splinefun()? ...
1
vote
0answers
96 views

Line smoothness/waviness

I am working on a project which requires me to watch video of athletes and measure the straightness/smoothness/waviness, whatever term is acceptable, of their spine. Dividing the spine into segments ...
0
votes
2answers
1k views

Exponential regression trendline does not match data

I'm attempting to generate an exponential regression equation using Excel 2010. I plan to use the equation to predict the future condition of roads. I've mocked up a simple chart in Excel using the ...
0
votes
1answer
40 views

Normal distribution curve percentages

Lets assume I’m grading following a normal distribution but instead of having a standard grading scale from A to F I have a grading scale from A to J with no plus or minus. Whats the percentage for ...
0
votes
2answers
206 views

Describe a curve by other than formula, fitting or interpolation

I have a curve defined by a set of $(x,y)$ given points. After ploting these points I get : My aim is to study the sensitivity of the operation that results these points. In order to do that, the ...
0
votes
1answer
36 views

Name of type of curve that uses x value as a divisor for y

What is (or is there) a name of a curve that is on X and Y axis, where the Y value is divided by X? For example, Y at X being 1 = 100, Y at 2 = 100/2 Y at 3 = 100/3. The type of curve I am thinking ...
0
votes
1answer
718 views

ROC AUC and PR AUC: Are the AUC values different for each class?

When dealing with a binary classification problem, where the decision function threshold is being varied from 0 to 1 at step 0.1: When calculating the Area Under the Curve (AUC) for a ROC Curve plot (...
0
votes
1answer
97 views

Vertically translated depreciation curve: Update the exponential regression coefficient

I have an exponential regression equation that I use to predict the condition of roads. The equation can be found on page 53 of the original master's thesis: Development of a Flexible Framework for ...
0
votes
0answers
30 views

Similarity of form of two curves

Currently I'm working on a project on finding out the similarity of two movies based on the sentiment analysis I did on their subtitles. I measured the sentiment of each individual sentence and paired ...