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5
votes
2answers
577 views

ListContourPlot interpolation screws up on concave set of data

I want to create ListContourPlots for sets of Data (from a physics simulation) given as Triplets {x, y, f(x, y)}. Certain parameter regions in the x-y-plane are ...
2
votes
1answer
496 views

Importing data sets from plain-text files and performing operations on them

I am working with a lot of daily weather files in the txt format. I need to calculate a daily quantity from each of them, e.g., daily light intensity, which ...
3
votes
1answer
519 views

Read and filter a text file without importing

I have a large text file of a million sections. Each section contains A lines of header and B lines of numeric data. I want to read the first and last line of B from each section (to have a list of 2 ...
8
votes
3answers
772 views

Approximately Fit Data Without FindFit

I have some noisy data, and I'd like to analyze the derivative of the function the data approximately matches. Interpolation is normally great, but doesn't work ...
2
votes
1answer
133 views

Plot[] breaks behavior of custom data handling function - Recursion

I am working on a utility to analyze a set of data. I want to process the data with a sliding window, in such a way that there is an output associated with each sample of data. To start, I have a ...
19
votes
4answers
1k views

How to integrate functions of linearly interpolated data?

At first, consider integration of pure InterpolatingFunction. Importing some data (works in v.9, for earlier versions one can use this link to download zipped ...
1
vote
0answers
94 views

ReadList and multiple access of the same file

I have a file containing a large amount of data which can be processed independently. In order to process all data in a reasonable amount of time I distribute the jobs on three different machines. ...
0
votes
3answers
413 views

How to export a header before the data in the result file?

I would like to export a phrase to my result data as a heading. I'm exporting the data correctly with Export["file.dat", table]. But I'm doing several ...
2
votes
3answers
250 views

Making data persistent, as in xmgrace

I've been using xmgrace for quite a long time as my favorite solution for scientific data manipulation and plotting. These data often come from home-made fortran programs, in the form of, e.g., a ...
1
vote
1answer
456 views

Optimizing the fitting of Ordinary Differential Equation(NDsolve) involving interpolation functions

I am a newbie to this forum. I am trying to use NDsolve to solve some ODEs involving the interpolation function. Then, I will compare the fitted curve and data to determine the ODE coefficients. ...
5
votes
1answer
276 views

LinearModelFit with millions of rows

I'd like to do a simple regression with millions of rows of (x,y) data. It seems to be too long for Mathematica. Is there a way to speed it up? It shouldn't be that hard to do, I am not sure what ...
3
votes
3answers
450 views

How do I make a frequency heatmap?

I have an array of data that has repeats in it. I want to generate a heatmap depending on how much repetition each point has, as in how many times it is repeated.
0
votes
1answer
366 views

importing and manipulating data file

I have a large text file containing numeric data of 1000 groups each of 200 lines. The lines are unsorted. There is a 9 line header at the beginning of each group, i.e., 209 ⨉ 1000 lines altogether. ...
12
votes
2answers
1k views

How do you deal with very large datasets in Mathematica?

This question is in two related parts. The first is about dataset size, the second data wrangling. Part 1: I've built a naive Bayesian classifier on Mathematica. It uses ...
3
votes
0answers
100 views

External file Sub Matrix Import

Is there a Built-In Mathematica Function to extract a Sub matrix from a huge external file? Functions getting pieces of internal nested Lists, (arrays) are in place. Example: ...
5
votes
2answers
2k views

How do I plot the derivative of a set of experimental points?

I have a set of points like this: P = {{$x_1$,$y_1$},{$x_2$,$y_2$},...,{$x_n$,$y_n$}}. I want to plot them and also plot the derivative of that graph. How can I do this with Mathematica? Is there a ...
8
votes
3answers
802 views

Analytically finding critical values in a hysteresis curve made with ListPlot

Let me start with a super basic explanation of what I'm trying to do, and I will follow with a more detailed discussion afterwards. From data in the form shown below (a ...
14
votes
2answers
803 views

Dealing with large files

I have a *.dat file in which the contents are basically one giant list: {1,2,3,4} {5,6,7,8} {9,10,11,12} and so on. I'd like to read in the first 500 members { ...
28
votes
4answers
965 views

Filtering beat-to-beat heart rate data

From an experiment, I have a dataset of beat-to-beat heart rate data: a list of the time between each heart beat in [ms]. The data is measured using an infrared optic sensor at the finger tip. The ...
3
votes
0answers
261 views

How to save (large) data generated from simulations

The following is a simple example of a much larger simulation that I want to run Define some processes ...
0
votes
1answer
365 views

How to create function that classifies sample data

I want to create expression, that classifies samples ( 4 weather features -> decision). Example training data: For the values that i have data for, I can use rules: ...