interpolation

问题 Is there any way to plot 2D array as an image using Bokeh with interpolation like in Matplotlib? I am able to plot using an example: https://docs.bokeh.org/en/latest/docs/gallery/image.html However, the image is to coarse. I like the way interpolation work in Matplotlib: https://matplotlib.org/gallery/images_contours_and_fields/interpolation_methods.html I tried to perform interpolation beforehand but the matrix size now is to big. 回答1: If you are working with a large dataset then you could

问题 I have one data frame and one look up table. What I want is to compare df_dat$value with df_lookup$threshold . If the value falls into threshold range, then create a new column transfer in df_dat so that its values are linearly interpolated from the transfer column in df_lookup library(dplyr) df_lookup <- tribble( ~threshold, ~transfer, 0, 0, 100, 15, 200, 35 ) df_lookup #> # A tibble: 3 x 2 #> threshold transfer #> <dbl> <dbl> #> 1 0 0 #> 2 100 15 #> 3 200 35 df_dat <- tribble( ~date, ~value

问题 I need to construct an interpolating function from a 2D array of data. The reason I need something that returns an actual function is, that I need to be able to evaluate the function as part of an expression that I need to numerically integrate. For that reason, "interp2" doesn't cut it: it does not return a function. I could use "TriScatteredInterp", but that's heavy-weight: my grid is equally spaced (and big); so I don't need the delaunay triangularisation. Are there any alternatives? 回答1:

问题 This question is different from the previous question (How to find indices with a negative value and replace the value with the nearest index's value that happens to be positive?). The previous question was to replace an index's unwanted value with its nearest positive index's value on the same row . This question is to replace the unwanted value with its nearest positive index's value throughout the entire matrix (not only limited to the same row) . If there is more than one index that is

问题 I'm using opencv remap function to map an image to another coordinate system. However, my initial tests indicate that there are some issues with the interpolation. Here, I give a simple example of a constant 0.1 pixel shift for a image that is 0 everywhere but at position [50,50]. import cv2 import numpy as np prvs = np.zeros((100,80), dtype=np.float32) prvs[50:51, 50:51] = 1. grid_x, grid_y = np.meshgrid(np.arange(prvs.shape[1]), np.arange(prvs.shape[0])) grid_y = grid_y.astype(np.float32)

问题 [Screenshot below] I was using ListPlot to draw a smooth line through some data points. But I want to be able to work with the 1st and 2nd derivative of the plot, so I thought I'd create an actual "function" using Interpolation. But as you can see in the picture, it's not smooth. There are some strange spikes when I do Plot[Interpolation[...]...]. I'm wondering how ListPlot get's it's interpolated function, and how I can get the same thing, using Interpolation[] or some other method. thanks,

问题 I know how to find indices with a negative value from a matrix. matrix(matrix<0) = %something should be done; But don't know how to replace their values with the nearest index's value that happens to be positive. The nearest index here should be in the same row where the observed index is laid. If there is no index with a positive value in the row, 0 should be interpolated to every index of that row. If there is more than one index that is the nearest to the observed index in the same row,

问题 I know how to find indices with a negative value from a matrix. matrix(matrix<0) = %something should be done; But don't know how to replace their values with the nearest index's value that happens to be positive. The nearest index here should be in the same row where the observed index is laid. If there is no index with a positive value in the row, 0 should be interpolated to every index of that row. If there is more than one index that is the nearest to the observed index in the same row,

问题 I would like to visualise a VTK data file (OpenFOAM output) using python. The plot I would like to make is a 1-d line plot of a quantity between two endpoints. To do so, the unstructured data should be interpolated on the points which lie between the two endpoints. I've used the package Mayavi to visualise the VTK data. At the mayavi webpage there is a description of probing a single value from a scalarfield. This function does not work on a VTK file. Also I've found a delaunay3d method (mlab

问题 Background I have 4 sets of data for a brushed DC motor all collected from the same experiment : torque vs speed (T vs w) torque vs efficiency (T vs n) torque vs input power (T vs Pin) torque vs output power (T vs Pout) However, each data set has: slightly different x values for the first and last data pairs (T_0 and T_N do not match between each data set) different spacing between each data point (dT is not the same for all sets) different sizes ("T vs w" has more data pairs than "T vs Pin")