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How to Create a Draggable Line in HTML5 Canvas?

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问题 So if you draw a line on an HTML5 canvas, what is the best way to make it draggable onMouseDrag? I know you can do this very easily in SVG, but since the canvas is not as easy to work with, I would like to know a good solution to this. 回答1: Here's one way create draggable lines on html5 canvas. A Note about html5 canvas: You can't really move anything that has already been drawn on html5 canvas. Instead you simulate movement by clearing the canvas and redrawing everything in it's new position

plotly regression line R

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问题 Problem with adding a regression line to a 'plotly' scatter plot. I've done the following code: require(plotly) data(airquality) ## Scatter plot ## c <- plot_ly(data = airquality, x = Wind, y = Ozone, type = "scatter", mode = "markers" ) c ## Adding regression line (HERE IS THE PROBLEM) ## g <- add_trace(c, x = Wind, y = fitted(lm(Ozone ~ Wind, airquality)), mode = "lines" ) g 回答1: I reckon it's caused by the missing values airq <- airquality %>% filter(!is.na(Ozone)) fit <- lm(Ozone ~ Wind,

Why doesn't .rstrip('\n') work?

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问题 Let's say doc.txt contains a b c d and that my code is f = open('doc.txt') doc = f.read() doc = doc.rstrip('\n') print doc why do I get the same values? 回答1: str.rstrip() removes the trailing newline, not all the newlines in the middle. You have one long string, after all. Use str.splitlines() to split your document into lines without newlines ; you can rejoin it if you want to: doclines = doc.splitlines() doc_rejoined = ''.join(doclines) but now doc_rejoined will have all lines running

How to move cursor back to the first line in C?

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问题 I am new to C and this is my code. #include<stdio.h> void printCard(char name, char symbol); int main() { printCard('J','*'); printCard('K','&'); } void printCard(char name, char symbol) { printf("-------------\n"); printf("| %c |\n",name); printf("| %c |\n",symbol); printf("| |\n"); printf("| |\n"); printf("| |\n"); printf("| %c |\n",symbol); printf("| %c |\n",name); printf("-------------\n"); } This is the output that I am getting. Is there a way to get that second card to appear beside the

Find perpendicular line using points on that line

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问题 I have a line (P1, P2), and a point on that line (midpoint). What equation can I used to find the perpendicular line of line (P1, P2), that passes through midpoint. The point labelled with a '?' is unknown. I do not wish to use angles, only the 3 points given (P1, P2, midpoint). The line P1, P2 can be of any orientation/angle. Thanks in advance. 回答1: Let define vector D = P2 - P1 (dx=x2-x1, dy = y2-y1) and middle point mx = (x2+x1)/2 my = (y2+y1)/2 Perpendicular to D vector PD = (-dy, dx)

Run JavaScript in a Windows Command Line

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问题 This is something I only found out about today is that JavaScript can be run through a windows command line. So I found out that to run a javascript file in windows cmd.exe you use cscript. My hworld.js file only has one line print('hello world'); I try to run this through the command line with cscript /Prog/hworld.js It didn't run with the error Microsoft JScript runtime error: Object Expected Are there steps i need to follow before simply cscript running a one line javascript file. I was

windows Python3报错 ValueError: embedded null byte

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调用爬取推特的twint库时候代码报错： Traceback (most recent call last): File "D:/pycharm project/twint/wangjinyu.py", line 10, in <module> twint.run.Search(c) File "D:\pycharm project\twint\twint\run.py", line 288, in Search run(config, callback) File "D:\pycharm project\twint\twint\run.py", line 209, in run get_event_loop().run_until_complete(Twint(config).main(callback)) File "C:\Program Files\Python36\lib\asyncio\base_events.py", line 484, in run_until_complete return future.result() File "D:\pycharm project\twint\twint\run.py", line 150, in main await task File "D:\pycharm project\twint\twint\run.py",

Passing parameter to function in add.expr inside heatmap.2

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问题 I'm generating clustering heatmap with heatmap.2 function (R gplots package). I'd like to add a vertical line(s) onto the image at variable location(s) using add.expr parameter. For example, xx=replicate(10, rnorm(10)) # some random matrix heatmap.2(xx, trace="none", add.expr=abline(v=c(3.5,6.5), lwd=3)) This works great. The problem is it doesn't work if I pass the lines location as a variable: linePosition = c(3.5,6.5) heatmap.2(..., add.expr=abline(v=linePosition, lwd=3)) It looks like

C# (sharp) reading random line from txt file [duplicate]

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问题 This question already has answers here : Read random line from a file? c# (2 answers) Closed 6 years ago . Can anyone tell me how to read random line from txt file? I want to read random line from txt file and show only that line in textBox. Code examples would be great! Thanx in foward 回答1: var lines = File.ReadAllLines(path); var r = new Random(); var randomLineNumber = r.Next(0, lines.Length - 1); var line = lines[randomLineNumber]; 回答2: The simplest solution is to read all the lines to

C# (sharp) reading random line from txt file [duplicate]

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