Stack Overflow
Stack Overflow

Questions tagged [threshold]

The starting point for a new state.

715 questions
4
votes
1 answer

Improve Text Binarization / OCR Preprocessing with OpenCV

I am building a scanner feature for my app and binarize the photo of the document with OpenCV: // convert to greyscale cv::Mat converted, blurred, blackAndWhite; converted = cv::Mat(inputMatrix.rows, inputMatrix.cols, CV_8UC1); …
Pascal
  • 2,590
  • 3
  • 21
  • 46
4
votes
0 answers

Defining a threshold for feature matching in geometrical re-ranking

I'm implementing a cache for virtual reality applications: given an input image query, return the result associated to the most visually similar cached image (so a previously processed query) if the distance between the query representation and the…
justHelloWorld
  • 6,478
  • 8
  • 58
  • 138
4
votes
3 answers

calculate number of rows in a dataframe above threshold as a function or other column factors

I would like to get find the number for rows for each subject for each day where the value is greater than 11 and output these in a data frame for analysis. The data set is large (5000 rows) so need a function for this. subject = c(rep("A", 12),…
MLyall
  • 119
  • 9
4
votes
2 answers

Why is image binarization showing poorer results?

Please, refer to this journal article. The last paragraph of the section 4.1 (Preprocessing) says that, Using [threshold = (mean + std dev)] along with Otsu Thresholding gives the following result, . And, without them I obtain the following…
user366312
  • 16,949
  • 65
  • 235
  • 452
4
votes
0 answers

Threshold for TF-IDF cosine similarity scores

This question is very similar to this one: Systematic threshold for cosine similarity with TF-IDF weights How should I cut off tiny similarities? In the link above, the answer gives a technique based on averages. But this could return documents even…
Guilherme Caminha
  • 324
  • 1
  • 16
4
votes
4 answers

Damerau - Levenshtein Distance, adding a threshold

I have the following implementation, but I want to add a threshold, so if the result is going to be greater than it, just stop calculating and return. How would I go about that? EDIT: Here is my current code, threshold is not yet used...the goal is…
CaffGeek
  • 21,856
  • 17
  • 100
  • 184
4
votes
3 answers

How threshold images with texture? Recognition by tesseract

Source image: Destination image: Code: cv::Mat sharpenedLena; cv::Mat kernel = (cv::Mat_(3, 3) << 0, -1, 0, -1, 5, -1, 0, -1, 0); cv::filter2D(matGrey, sharpenedLena, matGrey.depth(), kernel); cv::adaptiveThreshold(sharpenedLena, matBinary,…
hnzlk2015
  • 43
  • 3
4
votes
1 answer

python's negative threshold, the lowest non-infinity negative number?

What is python's threshold of representable negative numbers? What's the lowest number below which Python will call any other value a - negative inifinity?
user961627
  • 12,379
  • 42
  • 136
  • 210
4
votes
1 answer

tracking multiple objects by color OpenCV 2.x

Currently i am trying to track multiple objects by color. I've based on documentation code. import cv2 import numpy as np cap = cv2.VideoCapture(0) while(1): # Take each frame _, frame = cap.read() # Convert BGR to HSV hsv =…
alejandro zuleta
  • 13,962
  • 3
  • 28
  • 48
4
votes
3 answers

Does a Neural Network with Sigmoid Activation use Thresholds?

I'm a tad confused here. I just started on the subject of Neural Networks and the first one I constructed used the Step-Activation with thresholds on each neuron. Now I wan't to implement the sigmoid activation but it seems that this type of…
Marnix v. R.
  • 1,638
  • 4
  • 22
  • 33
3
votes
3 answers

R Is there a way to do thresholding in linear regression?

I'm trying to do a linear regression but I'm only looking to use variables with positive coefficients (I think this is called hard-thresholding, but I'm not certain). for example: > summary(lm1) Call: lm(formula = value ~ ., data = intCollect1[,…
screechOwl
  • 27,310
  • 61
  • 158
  • 267
3
votes
3 answers

niblack thresholding

I am trying to implement the niblack thresholding algorithm which uses the formula: pixel = ( pixel > mean + k * standard_deviation ) ? object : background where k has standard value 0. Could someone please tell me how to implement this in matlab?…
NeedHelp
  • 101
  • 3
  • 9
3
votes
1 answer

Cumulative sum with a threshold window in R data.table

I want to calculate the rolling sum of n rows in my dataset where the window size 'n' depends on the sum itself. For example, I want to slide the window as soon as the rolling sum of time exceeds 5 mins. Basically, I want to calculate how much…
srishti
  • 31
  • 3
3
votes
1 answer

R: Find cutoffpoint for continous variable to assign observations to two groups

I have the following data Species <- c(rep('A', 47), rep('B', 23)) Value<- c(3.8711, 3.6961, 3.9984, 3.8641, 4.0863, 4.0531, 3.9164, 3.8420, 3.7023, 3.9764, 4.0504, 4.2305, 4.1365, 4.1230, 3.9840, 3.9297, 3.9945, 4.0057, 4.2313, 3.7135,…
OCSee
  • 35
  • 8
3
votes
1 answer

Creating Datadog alerts for when the percentage difference between two custom metrics goes over a specified percentage threshold

My current situation is that I have two different data feeds (Feed A & Feed B) and I have created custom metrics for both feeds: Metric of Order counts from Feed A Metric Order counts from Feed B Next steps is to create alert monitoring for the…
novicedeveloper
  • 31
  • 1
  • 2
1 2 3
…
47 48