FAQ Database Discussion Community

## Inverse Distance Weighting in R

r,csv,coordinates,interpolation
Trying to interpolate a set of data using IDW. I am able to bring in the csv and convert it to a spatial points data frame. My column headings are lat and lon instead of x and y. The coordinates are very minimal in distance due to the csv being...

## Problems interpolating and evaluating numpy array at arbitrary points with Scipy

python,scipy,interpolation
I am trying to replicate some of the functionality of Matlab's interp2. I know somewhat similar questions have been asked before, but none apply to my specific case. I have a distance map (available at this Google drive location): https://drive.google.com/open?id=0B6acq_amk5e3X0Q5UG1ya1VhSlE&authuser=0 Values are normalized in the range 0-1. Size is 200...

## Haskell Yesod: How to read text from file and apply variable interpolation to its content?

I have quite big markdown text hardcoded inside my handler function currently. To render it I use whamlet quasiquoter and Text.Markdown.markdown from markdown package: let md :: L.Text md = "#Some markdown stuff" authLayout \$ [whamlet| <div .StaticContent> #{markdown def md} |] There are some hardcoded links in the text...

## Escape characters appearing in an array with the `p` method without interpolation

ruby,string,interpolation,string-interpolation
For overflow below, the quotes are surrounding an array. overflow = [5,6,7] p overflow #=> [5, 6, 7] p "#{overflow}" #=> "[5, 6, 7]" For stack below, the results are strange for the interpolated expression. stack = 1234.to_s.chars.reverse.each_slice(3).map { |s| s.reverse.join }.reverse p stack #=> ["1", "234"] p "#{stack}" #=>...

## SciPy: n-dimensional interpolation of sparse data

python,optimization,numpy,scipy,interpolation
I currently have a collection of n-dimensional data points, each with a value associated with it (n typically will range from 2 to 4). I would like to employ some form of non-linear interpolation on the data points I am supplied with so that I can try and minimise this...

## MATLAB - Only plot a spherical section of data set which is cubic

matlab,plot,interpolation
I have a physics model that simulates a few things in a radius of 5000 km around an object in spherical coordinates. I found no way to interpolate spherical coordinates in MATLAB so I changed them to Cartesian with sph2cart function. Then I used scatteredinterpolant function with a 10000 by...

## Interpolate (or extrapolate) only small gaps in pandas dataframe

python,pandas,interpolation,extrapolation
I have a pandas DataFrame with time as index (1 min Freq) and several columns worth of data. Sometimes the data contains NaN. If so, I want to interpolate only if the gap is not longer than 5 Minutes. In this case this would be a maximum of 5 consecutive...

## Matlab Interpolation of 4D matrix

matlab,interpolation
I would like to interpolate 4D matrix. The matrix size is 400X200X400X200 of complex numbers. Im using the function: interpn And for that I have to set set my new grid by using: ndgrid But ndgrid takes hours. Can you please help? Thanks! Sample code: [Y X V U]=ndgrid (ky_vec,kx_vec,kv_vec,ku_vec);...

## Python interpolation of 3D data set

python,data,interpolation
Does anyone know how to interpolate a 3D data set with Python? I would like to interpolate in the x, y, and z dimension to obtain the correct value of the 4th column. Thanks a lot! The data looks like the following: x y z 75 1E+00 3.7594E-10 1.0199E-08 75...

## Dynamically create Ruby variables with string interpolation [duplicate]

ruby,variables,interpolation
This question already has an answer here: How to dynamically create a local variable? 1 answer I want to do something like: 4.times do |n| "member#{n}" = Fabricate(:user) end Calling member1, member2 etc.. would give me user instances. Is #send or #eval useful to my situation? Thanks for looking....

## scipy: interpolation, cubic & linear

python,scipy,interpolation
I'm trying to interpolate my set of data (first columnt is the time, third columnt is the actual data): import numpy as np import matplotlib.pyplot as plt from scipy.interpolate import interp1d data = np.genfromtxt("data.csv", delimiter=" ") x = data[:, 0] y = data[:, 2] xx = np.linspace(x.min(), x.max(), 1000) y_smooth...

## bi-linear interpolation zoom [duplicate]

matlab,zoom,interpolation
This question already has an answer here: Resize an image with bilinear interpolation without imresize 1 answer here, i want to zoom in my image(gray) using bi-linear interpolation method, but i not able generate final out put image properly,here is the matlab code : I = imread('house.png'); %image i...

## Mapping and linking model instances in a Rails show view

ruby-on-rails,ruby,model-view-controller,dictionary,interpolation
I have a scenario where an album has many tracks and the tracks have the possibility to have featured artists, also know as artists. The associations are setup just fine but its mainly my view code that suffers from major verbosity: <table> <% @album.tracks.each do |track| %> <td> <%= raw...

## Interpolating Gridded 3D Data to a finer scale

r,interpolation,spatial,grid-layout,netcdf
I have a NetCDF file of a probability surface. It's a 30x30 grid of 0.25 degree lat/lon intervals with a probability surface described in the z dimension. I can easily import this into Panoply, a NetCDF viewer: And it's then a breeze (checking one box) to interpolate/smooth the raw data...

## Matlab: non-monotonic interpolation

matlab,interpolation
I'm having a problem with interpolation from a non-monotonic function. x=[34,35,36,37,38,39,41,42,43,44,45,46] y=[0.33 0.166 0.25 0.33 0.5 0.58 0.66 0.66 0.5 0.58 0.8 0.66] I want to be able to interpolate the X value that corresponds to a Y value of 0.25. When plotting (x,y) I can see that there are...

## Polyfit and polyval to perform interpolation

matlab,interpolation,interpolate,function-interposition
I have x = linspace(-5,5,256) y = 1./(1+x.^2) plot(x,y,'...') %plot of (x,y) I want to estimate this with a polynomial of order 10, such that the polynomial intersects the graph at 11 points. So, I did this: x2 = linspace(-5,5,11) y2 = 1./(1+x2.^2) p = polyfit(x2,y2,10) %finds coefficients of polynomial...

## numpy interp decreasing xp

python,numpy,interpolation
I want to interpolate a numpy array, and the np.interp does almost exactly what I want: interp(x, xp, fp, left=None, right=None) One-dimensional linear interpolation. Except for this bit: Does not check that the x-coordinate sequence `xp` is increasing. If `xp` is not increasing, the results are nonsense. My xp is...

## NumPy analog of R's `filter`

python,r,numpy,interpolation
What is analog of R's filter in NumPy? I have the following R code: f <- rep(1/9, 9) smth_x <- filter(x, f, sides=2) Where x is some 1-D timeseries vector which may contain nan's. How to perform the same operation using NumPy? (or any other python libs)...

## interpolation/lookup in R

r,gps,interpolation,lookup
I'm switching to R from excel and was wondering how to do this in R. I have a dataset that looks something like this: df1<-data.frame(Zipcode=c("7941AH","7941AG","7941AH","7941AZ"), From=c(2,30,45,1), To=c(20,38,57,8), Type=c("even","mixed","odd","mixed"), GPS=c(12345,54321,11221,22331)) df2<-data.frame(zipcode=c("7914AH", "7914AH", "7914AH", "7914AG","7914AG","7914AZ"), housenum=c(18, 19, 50, 32, 104,11)) First dataset contains zipcode, house number range (from and to), type meaning...

## What interpolation technique does Matlab plot function use to show the data?

matlab,plot,interpolation
It seems to be very basic question, but I wonder when I plot x values against y values, what interpolation technique is used behind the scene to show me the discrete data as continuous? Consider the following example: x = 0:pi/100:2*pi; y = sin(x); plot(x,y) My guess is it is...

## Integrating Velocity Over a Complex 2-D Surface

matlab,interpolation,triangulation,numerical-integration
I'm using matlab to calculate the the average velocity in the cross section of a pipe by integrating discrete velocity points over a surface. The points are scattered in a random pattern that form a circle (almost). I used scatteredinterpolant to create a function relating x and y to v...

## icCube - InterpolateRGBColors based on min & max values?

colors,mdx,interpolation,iccube
I understand that InterpolateRGBColors function is returning a color by position of value between 0 and 1... So its seems to be doable only with percentages, not numbers... Is there a way to have the same functionality, but based on the min and max values returned in a set ?...

## Animate custom object variable

android,animation,interpolation
Let's say I have a custom object, like a Point class (I am not using the one from Android), and I need to slowly change its coordinates from a start value to an end value when the user double taps the screen. I have already all setup, but I can't...

## Limiting interpolation function to NA values

r,interpolation,zoo,spline
I am trying to use na.spline, part of the zoo package, to replace NA values in some imported speed data with a cubic spline interpolated values. na.spline is modifying the NA values as it is supposed to; however, it is also modifying values that originally equaled 0. ex <- data.frame(speed)...

## Best way to interpolate a numpy.ndarray along an axis

python,arrays,optimization,numpy,interpolation
I have 4-dimensional data, say for the temperature, in an numpy.ndarray. The shape of the array is (ntime, nheight_in, nlat, nlon). I have corresponding 1D arrays for each of the dimensions that tell me which time, height, latitude, and longitude a certain value corresponds to, for this example I need...

## How do I write an iterative version of my recursive function?

c,arrays,recursion,signal-processing,interpolation
I have a function that takes a large array of long doubles (65536 elements) and performs a bunch of mathematical operations to each element which ends up with a modified array which is then returned to main. The problem is, it is recursive and with so many elements, the program...

## 2D Matrix Rotation with Bilinear Interpolation

c,arrays,math,matrix,interpolation
I am having difficulty implementing Bilinear Interpolation of a rotated image. The image is represented as doubles in a 2D matrix. Below is the code I have been using. The image rotates correctly by the desired angle, however the interpolation does not seem to eliminate the 'jaggedness' of the output...

## Storing and accessing a piecewise interpolant using a single handle

matlab,interpolation,handle,curve-fitting,piecewise
I have a dataset containing two vectors of points, X and Y that represents measurements of an "exponential-like" phenomenon (i.e. Y = A*exp(b*x)). When fitting it with an exponential equation I'm getting a nice-looking fit, but when I'm using it to compute things it turns out that the fit is...

## Polyfit for more than one variable?

matlab,interpolation
Does it exists a function similar to polyfit to interpolate n variables? polyfit use x, y, N, where N is the degree, instead I would like to use x, y, z, and N. Any idea?

## How do I add missing rows AND interpolated value to a data frame in R?

r,interpolation
I have a table of data like this: dat <- data.frame( age = c(0,10,20,40,70,100), surv = c(1.0,0.9,0.8,0.6,0.3,0.0) ) I would like to add a row for every age that is missing (30,50,60,80,90) and then I would like to add the linear interpolation for surv to the new row. So the...

## Difference in x,y parameters for scipy interpolate RectBivariateSpline and interp2d

python,scipy,interpolation
If I want to interpolate the data below: from scipy.interpolate import RectBivariateSpline, interp2d import numpy as np x1 = np.linspace(0,5,10) y1 = np.linspace(0,20,20) xx, yy = np.meshgrid(x1, y1) z = np.sin(xx**2+yy**2) with interp2d this works: f = interp2d(x1, y1, z, kind='cubic') however if I use RectBivariateSpline with the same x1,...

## Unity3D Linear interpolation from V1 to moving V2

vector,unity3d,interpolation
I posted this question on the stack math site, but they are not too excited to see questions including programming. Anyway, now I am here :) I have an object, which is located at MyTransform.position (Vector) That object should follow the DesiredPosition (Vector), which is moving in varius directions with...

## Spline interpolation with R

r,interpolation,spline
I want to perform a (cubic) spline interpolation for population data to "transform" yearly data into quarterly data. I know that there are a fair number of flaws doing so, but I need to do it. Here is an example of my code (using generic input data): #--------------spline interpolation x...

## Interpolation with Delaunay Triangulation (n-dim)

python,scipy,interpolation,delaunay
I would like to use Delaunay Triangulation in Python to interpolate the points in 3D. What I have is # my array of points points = [[1,2,3], [2,3,4], ...] # my array of values values = [7, 8, ...] # an object with triangulation tri = Delaunay(points) # a set...

## Interpolate 3d Data in Matlab

matlab,interpolation
I have a 7426x32 2D array of data from a 1deg cylindrical slice. It contains: X,Y,Z, and a 29 variables such as temperature, density, pressure, etc. There are 79 mesh nodes in the X direction, 2 in the Y, and 47 in the Z. It's one 'line' of cell volumes...

## Matlab - Interpolation over a 3D surf with matrix, nonuniform, scattered data

matlab,plot,3d,interpolation
I am currently trying to interpolate the following surface plot in order to add more point and make it more smooth: hSurf = surf(X,Y,Z) with X,Y and Z all being matrices of size nXm. When looking for a solution, I have found the function griddata but I have found only...

## Interpolating variables within already interpolated strings in angular

javascript,angularjs,interpolation
I have the following arrangement to fetch helptexts from a single Coffeescript file. Coffeescript: help.ex: '{{example.variable}} identifies enterprise data centers' HAML: %example-directive(attr='{{help.ex}}') Now the example.variable is accessible but it is not getting interpolated on the view. This I guess is happening because the string as a whole is getting interpolated...