Stack Overflow
Stack Overflow

Questions tagged [threshold]

The starting point for a new state.

715 questions
3
votes
1 answer

R: Find consecutive values beneath threshold

I need to find consecutive values in a data.frame of wind speed measurements that are smaller than a certain threshold. I'm looking for 2 consecutive observations beneath the threshold. I want to return the location of the first observation of the…
ChrM
  • 61
  • 3
  • 12
3
votes
1 answer

sox effect: retriggerable silence

To detect speech I'm playing with this sox command: rec voice.wav silence 1 5 30% 1 0:00:02 30% It should start recording whenever the input volume raises about the threshold of 30% and stops after 2 seconds the audio falls below the same…
Mark
  • 4,338
  • 7
  • 58
  • 120
3
votes
3 answers

PostgreSQL calculate threshold query

i have postgresql db with a table t1 and i want to calculate a threshold. the threshold should be for example car 1 uses more fuel than 75 % of all cars, car2 uses more fuel than 50% of all cars, .... mathematically i understand what i want to do,…
fabvys
  • 413
  • 1
  • 5
  • 12
3
votes
3 answers

ImportError: No module named pyplot - Opencv

I am trying to execute the following code: import cv2 import numpy as np import matplotlib.pyplot as plt img = cv2.imread('Paw01.png',0) img = cv2.medianBlur(img,5) ret,th1 = cv2.threshold(img,127,255,cv2.THRESH_BINARY) th2 =…
Lucas
  • 63
  • 1
  • 5
3
votes
1 answer

How to change threshold for precision and recall in python scikit-learn?

I have heard people saying you can adjust the threshold to tweak the trade-off between precision and recall, but I can't find actual example of how to do that. My code: for i in mass[k]: df = df_temp # reset df before each loop #$$ #$$ …
KubiK888
  • 4,377
  • 14
  • 61
  • 115
3
votes
1 answer

First key in OrderedDict that exceeds threshold

Say I have an OrderedDict: a = OrderedDict([(5, 'a'), (7, 'b'), (10, 'c')]) Is there an efficient way to get the first value whose key exceeds a certain threshold, without looping over all keys? Examples: >>> get_first(a, 6) 'a' >>> get_first(a,…
user3446746
  • 141
  • 1
  • 12
3
votes
0 answers

How many thresholds and distance matrix are in Eigenface?

I edited my question trying to make it as short and precise. I am developing a prototype of a facial recognition system for my Graduation Project. I use Eigenface and my main source is the document Turk and Pentland. It is available here:…
Marcelo Cuadrado
  • 82
  • 7
3
votes
2 answers

Find threshold cross in Matlab timeseries data, then ignore subsequent crosses for 60 seconds before finding next threshold cross

This is a little complicated to explain. I have time series data formatted like this: https://docs.google.com/spreadsheets/d/1B8mN0uD-t4kQr2U20gS713ZFHN6IgGB7OMR3-pqJjrw/edit?usp=sharing That data represents voltage recordings at .01s intervals.…
user3746901
  • 73
  • 1
  • 5
3
votes
1 answer

How to chose the optimal HSV values for InRange thresholding in OpenCV

I have two related questions: I'm doing color object detection in OpenCV with the inRange threshold function. I'm getting excellent results if I manually choose the lower and upper HSV bounds, but this is very sensitive to the lighting conditions.…
My other car is a cadr
  • 1,429
  • 1
  • 13
  • 21
3
votes
3 answers

Otsu Thresholding on a Sobel Filtered Image gives different Results

I'm creating a Sudoku solving application on an Android platform and I've run into an issue when processing the image. I'm trying to find the horizontal lines of the puzzle using OpenCV using a Sobel filter and then thresholding with the Otsu…
user3577715
  • 31
  • 4
3
votes
2 answers

How to detect sign change (eg, positive to negative) in time series data?

I have data of fluxes over time and would like to obtain a list of times when the flux changed from negative to positive or vice versa. This seems like a simple thing so it probably has a simple answer but I haven't been able to find one with my…
DirtStats
  • 559
  • 9
  • 29
3
votes
1 answer

Object detecting using thresholding

I'm working on a program in matlab to detect an object in a sequence of images. The object I'm trying to detect a red ball. First, I tried to use thresholding to segment the ball from the image, but I couldn't do that. I couldn't get rid of the…
N4LN
  • 95
  • 3
  • 10
3
votes
1 answer

Finding several regions of interest in an array

Say I have conducted an experiment where I've left a python program running for some long time and in that time I've taken several measurements of some quantity against time. Each measurement is separated by some value between 1 and 3 seconds with…
user3394391
  • 487
  • 6
  • 15
3
votes
1 answer

OpenCV - Using ROI after a cvtColor

I am doing some ellipse recognition in an image and in order to do so I am opening a simple image: img = imread("M:/Desktop/PsEyeRight.jpg", CV_LOAD_IMAGE_COLOR); selecting a ROI (that's the only way I could see to set a ROI in OpenCV 2.4.6 where…
Michel Feinstein
  • 13,416
  • 16
  • 91
  • 173
3
votes
1 answer

opencv/python : motion detect weird thresholding

I am trying to make a motion detect program using my webcam, but I'm getting this weird results when thresholding the difference of frames: When Im moving: (seems okay I guess) ![enter image description here][1] When Im not moving: ![enter image…
Cap.Alvez
  • 1,363
  • 3
  • 17
  • 19
1 2 3
…
47 48