precision

Why is the output of inv() and pinv() not equal in Matlab and Octave?

由 孤街醉人 提交于 2019-12-09 03:29:11
问题 I have noticed that if A is a NxN matrix and it has the inverse matrix. But what the inv() and pinv() function output is different. - My environment is Win7x64 SP1, Matlab R2012a, Cygwin Octave 3.6.4, FreeMat 4.2 Have a look at the examples from Octave: A = rand(3,3) A = 0.185987 0.192125 0.046346 0.140710 0.351007 0.236889 0.155899 0.107302 0.300623 pinv(A) == inv(A) ans = 0 0 0 0 0 0 0 0 0 It's all the same ans result by running the same command above in Matlab. And I calculate inv(A)*A or

What is c printf %f default precision?

由 ↘锁芯ラ 提交于 2019-12-09 03:03:34
问题 I'm curious: If you do a printf("%f", number); what is the precision of the statement? I.e. How many decimal places will show up? Is this compiler dependent? 回答1: The ANSI C standard, in section 7.19.6.1, says this about the f format specifier: If the precision is missing, 6 digits are given 回答2: The default precision for %f is 6 digits (see ISO C99 specification, 7.19.6.1/7). 回答3: The book, C: A Reference Manual states that if no precision is specified then the default precision is 6 (i.e. 6

What's the right way to parseFloat in Java

由 纵然是瞬间 提交于 2019-12-09 02:56:42
问题 I notice some issues with the Java float precision Float.parseFloat("0.0065") - 0.001 // 0.0055000000134110451 new Float("0.027") - 0.001 // 0.02600000000700354575 Float.valueOf("0.074") - 0.001 // 0.07399999999999999999 I not only have a problem with Float but also with Double . Can someone explain what is happening behind the scenes, and how can we get an accurate number? What would be the right way to handle this when dealing with these issues? 回答1: The problem is simply that float has

OpenCL Floating point precision

由 痞子三分冷 提交于 2019-12-08 23:35:34
问题 I found a problem with host - client float standard in OpenCL. The problem was that the floating points calculated by Opencl is not in the same floating point limits as my visual studio 2010 compiler, when compiling in x86. However when compiling in x64 they are in the same limit. I know it has to be something with, http://www.viva64.com/en/b/0074/ The source I used during testing was: http://www.codeproject.com/Articles/110685/Part-1-OpenCL-Portable-Parallelism When i ran the program in x86

Changing precision of numeric column in Oracle

由 喜你入骨 提交于 2019-12-08 22:53:44
问题 Currently I have a column that is declared as a NUMBER. I want to change the precision of the column to NUMBER(14,2). SO, I ran the command alter table EVAPP_FEES modify AMOUNT NUMBER(14,2)' for which, I got an error : column to be modified must be empty to decrease precision or scale I am guessing it wants the column to be empty while it changes the precision and I don't know why it says we want to decrease it while we are increasing it, the data in the columns can't be lost. Is there a

Why does java.awt.Point provide methods to set and get doubles but store x and y as int's?

由 感情迁移 提交于 2019-12-08 19:26:46
问题 As you can see in the Oracle Documentation for java.awt.Point, x and y are stored as int . However, getX and getY return double . While there is a setLocation method that takes 2 double types, there is no constructor that does. Furthermore, the double gets truncated to an int internally anyway. Is there a good reason for this? You might avoid a cast on setLocation by having a method that takes double types, but you have the opposite problem when you call getX and getY . There's also a

Difference between double- precision data type and numeric data type

由 做~自己de王妃 提交于 2019-12-08 19:23:22
问题 What is the significant difference between double-precision data type and numeric data type in R programming? 回答1: From stat.ethz.ch: It is a historical anomaly that R has two names for its floating-point vectors, double and numeric (and formerly had real). double is the name of the type. numeric is the name of the mode and also of the implicit class. As an S4 formal class, use "numeric". The potential confusion is that R has used mode "numeric" to mean ‘double or integer’ We can think of

Convert between Degree and Milliseconds

由 故事扮演 提交于 2019-12-08 18:25:32
I know the formular for conversion from Degree to Milliseconds and vice-versa. It can be implemented like that: protected function decimal_to_milisecond($dec) { if (!empty($dec)) { $vars = explode(".",$dec); if (count($vars) == 2) { $deg = $vars[0]; $tempma = "0.".$vars[1]; $tempma = $tempma * 3600; $min = floor($tempma / 60); $sec = $tempma - ($min*60); return round((((($deg * 60) + $min) * 60 + $sec) * 1000)); } else return false; } else return false; } function milisecond_to_decimal($sec) { if (!empty($sec)) { $s = $sec / 1000; $d = (int)($s / 3600); $s = $s % 3600; $m = (int)($s / 60); $s

JavaScript 64 bit numeric precision

由 妖精的绣舞 提交于 2019-12-08 18:00:50
问题 Is there a way to represent a number with higher than 53-bit precision in JavaScript? In other words, is there a way to represent 64-bit precision number? I am trying to implement some logic in which each bit of a 64-bit number represents something. I lose the lower significant bits when I try to set bits higher than 2^53. Math.pow(2,53) + Math.pow(2,0) == Math.pow(2,53) Is there a way to implement a custom library or something to achieve this? 回答1: Google's Closure library has goog.math.Long

Converting 8 bytes of little-endian binary into a double precision float

由 拟墨画扇 提交于 2019-12-08 15:06:55
问题 I have a binary file that I read byte by byte. I come across a section that is 8 bytes long, holding a double precision float (little endian). I can't figure out how to read this in and calculate it properly with masking and/or casting. (To be specific, the file type is .LAS, but that shouldn't matter). Are there any Java tricks? 回答1: You can use ByteBuffer from a byte[] bytes double d = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN ).getDouble(); from a Socket ByteBuffer bb =
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