c****u
发帖数: 584 | 1
~~~~~~~~~
What is this one?
M^2 is the sum of the square of the coefficients of Gaussian modes. So if
you decompose your beam to Gaussian modes, you get M^2. |
|
R***r
发帖数: 322 | 2 【 以下文字转载自 Physics 讨论区,原文如下 】
发信人: rover (小喽罗 --- 有来有去), 信区: Physics
标 题: Re: [转载] 有谁能说说Fourier变换？
发信站: Unknown Space - 未名空间 (Sat May 29 14:50:25 2004) WWW-POST
Decompose a complicated "function" into a linear composition
of simpler forms?
It helps to pick out the most important "factors" --- terms
with a large "coefficient/amplitude" that affect the overall
"shape" most.
As an example:
(My guess) one can do the "active noise cancelling" by figuring
out the frequencies of the largest amplitudes |
|
Z***U
发帖数: 216 | 3 个人觉得如果
1） Correlation matrix 的 off diagonal elements较大，也就是具有一定的 correl
ation
2） Factor 的数量选择相同的话， loading 给出的解释应该是大致差不多的，虽然具
体的数值可能会有差别。
是的，负值是在 prinit 或者 ml 时才可能得到的，因为iteration之后再用来
decompose的communality 矩阵可能不再是 positive definite。
因此，prin 更多的解释了standardized responses 的 variance，
而 prinit 和 ml 更多的考虑到 correlation，所以 loading 会有不同，但是如果数据
确实具有较强的correlation，比如 MSA 较大，那么所得的所有factor 的解释不会有
很大差别。 不过个别的 factor 则会有很大差别。 |
|
q**j
发帖数: 10612 | 4 i tried, unique won't work. here is another way:
> match(x[rank(x)%%1==0],x)
[1] 3 4
it should be easier if you decompose the above line into smaller bites. waiting for better ways ... |
|
D******n
发帖数: 2836 | 5 equal variance ba, constant means it is constant ...strange word...
also called homoscedasticity(so hard to pronounce....)
equal variance makes sure u can orthogonally decompose the SS and so that u
can use F test... |
|
b*******x
发帖数: 100 | 6 汗。。。
跟list不太是一回事儿。。。
常见的是s3 method，比如说，你用plot函数，根据传递的参数不同，会相应出来不同
的结果。你
只需要一个generic function来定义很多method，但是s3缺点是，没法validate参数的
class，命名方法不严谨
methods('plot')
[1] plot.acf* plot.data.frame* plot.Date*
[4] plot.decomposed.ts* plot.default plot.dendrogram*
[7] plot.density plot.ecdf plot.factor*
[10] plot.formula* plot.hclust* plot.histogram*
[13] plot.HoltWinters* plot.isoreg* plot.lm
[16] plot.medpolish* p |
|
q**j
发帖数: 10612 | 7 好象是要把A给decompose了，但是是哪种decomposition呢？ |
|
o****o
发帖数: 8077 | 8 this is ur chance to show your presentation skills
be structured, talk about the project at high level, address:
1. what this project is for (objective)
2. what did you do (statistical modeling, simple descriptive stat, etc)
3. what was the result and $ value of the project
then, decompose above points sequentially into more details.
1. Talk about the background of the project;
2. talk about details about your work, such as how did u define dependent
variable from business requirement if you use... 阅读全帖 |
|
F******n
发帖数: 160 | 9 In that case, it is not a trivial problem, but it could be done by applying
the incremental SVD algorithm.
This efficient/adaptive algorithm was originally given by a guy (Matthew)
from Mitsubishi research lab. You can easily google that paper.
The main point relevant to the LS regression:
b = (X'X)^(-1) (X'y) (1)
is that, matrix inversion (X'X)^(-1) is essentially an SVD problem. As your
new data come in, you should sort of have an updated X and y, and
consequently an updated X'X. In abov... 阅读全帖 |
|
d******e
发帖数: 7844 | 10 你确定你读懂计算了么? SCAD和MCP都只是对Penalty做LQA或者LLA,这两种penalty都是
decomposable的,根本不涉及到矩阵求逆.
SCAD和MCP的code,我都写过,无非就是多了一个Convex Relaxation的loop而已,如果是
做Onestep的SCAD,连loop都不需要写. |
|
S******y
发帖数: 1123 | 11 I have finally got Hadoop working on my Linux box. Next I would like to try
to see if I could to parallel model estimation for some commonly used models
such as logistic regression.
My question now is - how to paralell gradient descent for logistic model
estimation for real large data set?
Any thoughts would be greatly appreciated. Thanks in advance!
PS. See R code below. If needed, I could rewrite the following code in Java
or Python. But the question is how to decompose the following estimatio... 阅读全帖 |
|
t*****t
发帖数: 5 | 12 在R里, 如果采用ts的数据结构来保存数据, 用decompose命令后, 就可以得到含有
trend, seasonal, random三个components的时间序列分析结果。
现在我想在上面这三个compenents之外, 再加一个自定义的component。
这要如何实现呢？
谢谢！ |
|
S*******e
发帖数: 525 | 13 I tried to use R to decompose time series into Seasonal, Trend... but my
time series has some missing data. So it will produce
Error in na.omit.ts(x) : time series contains internal NAs
Any easy way to work around the problem? |
|
|
y**a
发帖数: 2546 | 15 不是这个行业的，不过好几年前正好给一个大公司做过一次 sales forecasting，作为
他们更换原来软件的benchmark
需要比较准确预测的话，我们当时基本就是 用time series 建模
1. 先分析数据pattern，关键是 对数据进行decompose 以后再看，比如 level,trend
,seasonality
2. 根据数据分析结果，选择合适的模型，软件的话可以用 SAS |
|
l******0
发帖数: 244 | 16 More generalized:
If 'school' is a categorical feature, with 4 possible values of [primary,
middle, high, college], how to represent an instance of school with value of
'middle'? The task is for regression or classification.
Two choices:
1) 1,2,3,4 represents primary, middle, high, college respectively, so the
middle school will be represented as [2]
2) an instance will be represented as a vector of [0, 1, 0, 0], where '1'
represents 'middle'. In this case, the original one feature are decompose... 阅读全帖 |
|
s**********8
发帖数: 25265 | 17 来自主题: MedicalDevice版 - FDA The Food and Drug Administration (FDA or USFDA) is an agency of the United
States Department of Health and Human Services, one of the United States
federal executive departments. The FDA is responsible for protecting and
promoting public health through the regulation and supervision of food
safety, tobacco products, dietary supplements, prescription and over-the-
counter pharmaceutical drugs (medications), vaccines, biopharmaceuticals,
blood transfusions, medical devices, electromagnetic radiati... 阅读全帖 |
|
s**********8
发帖数: 25265 | 18 Sterilization (microbiology)
http://en.wikipedia.org/wiki/Sterilization_(microbiology)
From Wikipedia, the free encyclopediaJump to: navigation, search This
article has multiple issues. Please help improve it or discuss these issues
on the talk page.
It may need reorganization to meet Wikipedia's quality standards. Tagged
since March 2008.
It is in need of attention from an expert on the subject. WikiProject
Microbiology may be able to help recruit one. Tagged since December 2010.
Contents [hide... 阅读全帖 |
|
a***a
发帖数: 12425 | 19 【侏罗纪公园】化石坑
看了一部纪录片，介绍了四个世界著名的化石坑，那里有着保存很完整的各种动植物化
石，这些化石使得我们对史前生态的重要阶段得以进行详细的分析了解，包括他们的外
观，内部构造，饮食习惯，社会生活等等。我看片子的时候做了些记录，上网查了查，
又存了些截屏图片，写个总结，也不知道符不符合征文的规定。如有错误疏忽遗漏或不
妥请指正。
(一) 伯吉斯页岩（Burgess Shale Formation），约五亿三千万年前
一九零九年，美国地质学家查尔斯•都利特•沃尔科特（Charles
Doolittle Walcott）在加拿大的洛基山脉进行野外探查，由于马摔跤无意间找到了一
块化石，随后他发现只有七英尺厚的伯吉斯页岩夹层是所有化石的出处。随后的两年内
，沃尔科特和他的儿子们共收集了六万一千多个样本，在所有发现中有三分之二是科学
新发现，包括以前从未有过的保存完整的软体动物化石。伯吉斯页岩的生物群种类相当
多，有食泥动物，滤食动物和掠食动物。沃尔科特直到一九二七年去世都在研究这些化
石，值得钦佩。
(二) 索伦霍芬石灰岩（Solnhofen... 阅读全帖 |
|
a***a
发帖数: 12425 | 20 CharlesSong网友提供的新概念英语上的La Brea Tar Pit文章。重温一下吧（虽然我以
前只看了Puma一篇文）。
【 以下文字转载自 History 讨论区 】
发信人: CharlesSong (每只猫咪都需要定期体检), 信区: History
标 题: 地球上的昔日生命(新概念英语第四册26课)
发信站: BBS 未名空间站 (Wed Sep 26 10:54:16 2012, 美东)
你提到的La Brea tar pit,想起来在高中学新概念英语的时候看到过，怀念一下年轻时
的岁月：
L. G. Alexander: New Concept English, Book IV
19/49
It is animals and plants which lived in or near water whose remains are
most likely to be preserved, for one of the necessary conditions of
preservation is quick burial, and it is only in ... 阅读全帖 |
|
r*****y
发帖数: 507 | 21 突然想起一个问题，
scale, rotation, translation, squash, etc...等可以最终相乘为一个
4*4 matrix MX.
Now, given an arbitrary 4*4 transformation matrix MX, and MX(4,1:4) = [ 0 0 0
1]; Can we decompose this matrix to all possible operations, such as scaling,
rotation etc... is it unique? or for some matrix, it doens't exist feasible
solution?
Any hint/link for this? thanks. |
|
p*******r
发帖数: 4048 | 22 I feel that I have a little bit of authority to say a few
words on this.
But you have to promise not to report me. :) I had some
friends who grew pot in high school. I also conducted a
little bit of federally sponsored pot research when I was an
undergraduate student. Basically, there is no known long
term side effect of pot but pot decomposes into about 100
compounds and only a few of those have been carefully
examined. The short term memory loss effect of pot is
well-documented. Recently a can |
|
