k******n
发帖数: 35 | 1 You did not mention why you need the inverse. Without this, others could not
help you much.
(1) At first, I have to ask do you really need the inverse?
The inverse matrix would be dense. I do not think you have enough memory to
manipulate it. Even you can compute this inverse, you have nothing to do
with it, since you have no idea how accurate it is. Most time, what you need
is the product of the inverse and a vector/matrix, say inv(A)*B. In some
cases, people want eigenvalues or singular values |
|
e**l
发帖数: 62 | 2 大概只知道inverse covariance matrix can tell conditional independence
structure.
本人不是统计也不是金融背景，只是计算数学，有方法弄出高维数据(multivariate
gaussian)的
inverse covariance matrix. 想找到在金融经济方面应用
大概两个大想法
1。需要用到inverse covariance matrix来算的公式
2.需要知道conditional dependence or not的金融模型或者简单问题
多谢大牛！！！ |
|
b********6
发帖数: 16 | 3 大坑，别跳了.....inverse scattering国内很多做的人都是数学系出身的，当然你要
去UIUC做inverse scattering还是可以的，那里氛围很好，不过大部分军方的项目不知
道你能不能做； 另外医学成像是Inverse scattering的出路之一了 |
|
e**l
发帖数: 62 | 4 大概只知道inverse covariance matrix can tell conditional independence
structure.
本人不是统计也不是金融背景，只是计算数学，有方法弄出高维数据(multivariate
gaussian)的
inverse covariance matrix. 想找到在金融经济方面应用
大概两个大想法
1。需要用到inverse covariance matrix来算的公式
2.需要知道conditional dependence or not的金融模型或者简单问题
个人猜想大概在风险计算方面有点用 不过所知甚少 希望大牛提点一二
多谢大牛！！！ |
|
w**********y
发帖数: 1691 | 5 Lots of statistical models need the inverse covariance matrix..
In finance, portfolio management uses it.
Google "inverse matrix optimal portfolio selection"
"inverse matrix optimal portfolio selection with Singular Covariance Matrix"
"Optimal mean-variance portfolio selection using Cauchy–Schwarz maximization"
In some basket products in credit, it should also be useful. |
|
e**l
发帖数: 62 | 6 大概只知道inverse covariance matrix can tell conditional independence
structure.
本人不是统计也不是金融背景，只是计算数学，有方法弄出高维数据(multivariate
gaussian)的
inverse covariance matrix. 想找到在金融经济方面应用
大概两个大想法
1。需要用到inverse covariance matrix来算的公式
2.需要知道conditional dependence or not的金融模型或者简单问题
多谢大牛！！！ |
|
c*********i
发帖数: 46 | 7 http://www.geeksforgeeks.org/counting-inversions/
给出了代码，可是看了程序后， 有点不解，想请大牛指教一下：
/*this is tricky -- see above explanation/diagram for merge()*/
inv_count = inv_count + (mid - i);
不应该是：
inv_count = inv_count + (mid - i)+1？
当copy a[j]时，left array 剩下的都是inversion,不应该是（mid - i）+ 1 个吗？
int merge(int arr[], int temp[], int left, int mid, int right)
{
int i, j, k;
int inv_count = 0;
i = left; /* i is index for left subarray*/
j = mid; /* i is index for right subarray*/
k = left; /*... 阅读全帖 |
|
i***e
发帖数: 3219 | 8 I saw a layer of stuff in the air above the valley floor today. Is this the
famous phenomenon of "inversion"? All right, the inversion is done, we're
going to achieve lasing action soon. |
|
w********s
发帖数: 59 | 9 这一组公式非常的牛。对一个toeplitz矩阵求逆可以变成对一组矩阵求和.可是我就是
找不到完整的表达式...跪求各位大牛的帮助...
看下面这一段话:
For a Toeplitz matrix T of order n + 1 the inverse matrix under some
conditions can be expressed explicitly via two of its columns. For
instance: for the expression via first and last columns the
condition is the (1,1) element of the inverse is not 0. |
|
w******g
发帖数: 15 | 10 sorry, I can not input chinese on this PC
I am doing instability analysis and I need to compute the inverse of a
matrix with size about 20000 by 20000
currently I do this using matlab, but it keep saying error ' out of memory'.
I have increased the PC memory to 4gb and tried all I can think of to free
up memory.
any one know about computation of inverse of large matrix? Is there any
better way to do it? comments will be appreciated! thanks! |
|
n**f
发帖数: 121 | 11 Assume I have a n*k matrix G where n>k. And I know rank(G) = k. According to
matrix theory G'G has full-rank and its inverse can be calculated. However
when I plug in the data to a numerical software, the software actually
complained that G'G is singular. For my problem, k is between 100 ~ 1000,
and
n is between 500 and 5000.
I manually wrote a C++ Gauss Elimination algorithm to verify that G'G has
rank
of k. But I notice that the Gauss Elimination algorithm would report the
matrix as singular... 阅读全帖 |
|
b****e
发帖数: 906 | 12 想知道有哪些经典的inverse problem和现在热门的题目，inverse problem常应用的领
域，有关典型的算法（这个也许太广了点）和这个领域中的着名人物。希望介绍不要太
偏重于数学。非常感谢 |
|
w********s
发帖数: 59 | 13 这一组公式非常的牛。对一个toeplitz矩阵求逆可以变成对一组矩阵求和.可是我就是
找不到完整的表达式...跪求各位大牛的帮助...
看下面这一段话:
For a Toeplitz matrix T of order n + 1 the inverse matrix
under some conditions can be expressed explicitly via two of its columns.
For instance: for the expression via first and last columns the condition is
the (1,1) element of the inverse is not 0. |
|
m***a
发帖数: 2 | 14 Hi,
I wonder how to compute the approximate inverse of a nonlinear operator. for
example, I have an operator, which convolve the input function with an
analytic function and then take the square of the convolution result. I
would like to find out the approximate inverse of such process.
does anyone know what book/papers describing such things?
Thanks
mlfma |
|
c*******v
发帖数: 2599 | 15 analytic function的Fourier级数和Chebyshev级数展开系数是指数下降的，
计算这种逆问题的时候只要记住不要用Taylor级数作就行了。
或者用待定系数法，或者取点值解代数方程组都可以。
Hi,
I wonder how to compute the approximate inverse of a nonlinear operator. for
example, I have an operator, which convolve the input function with an
analytic function and then take the square of the convolution result. I
would like to find out the approximate inverse of such process.
does anyone know what book/papers describing such things?
Thanks
mlfma |
|
s*****p
发帖数: 10 | 16 Each row of the matrix (M) below is from the Taylor series. I only need to
know the first three rows of the inverse of M. With fixed N, the inverse can
be obtained easily. I am wondering if there is a general solution to it.
Any suggestion is highly appreciated! |
|
b**g
发帖数: 335 | 17
乘法反元素
k在 mod n系统中的inverse就是l使得k*l=1 (mod n)
如n=5,则inverse table为
k k^(-1) |
|
d*******n
发帖数: 15 | 18 inverse的反函数还是inverse
那么JACOBIAN是正负1? |
|
a**********s
发帖数: 1075 | 19 modular multiplicative inverse是什么意思，如何计算
for example, how to find d ≡ e−1 (mod φ(n)), where d is the
multiplicative inverse of e (modulo φ(n))?
matlab里该如何计算? |
|
a**********s
发帖数: 1075 | 20 modular multiplicative inverse是什么意思，如何计算
for example, how to find d ≡ e−1 (mod φ(n)), where d is the
multiplicative inverse of e (modulo φ(n))?
matlab里该如何计算? |
|
a****o
发帖数: 42 | 21 For such large scale problem, before you do anything
concrete,
it might be a good thing to first try to find some way of
not
inverse the matrix.
Some thing you might consider:
1. If the matrix sparse? I guess it should be.
2. Are you really want to have a 1/A, or you just want an
answer to AX=b?
3. Except for symmetry, are their other characteristic you
can
exploit?
If all the answer is NO, perhaps what yhht said is right: do
the
inverse directly using some method, the reason is that for
such
la |
|
S******y
发帖数: 1123 | 22 I have a one-variable data set in R.
The plot of histogram of my numerical variable suggests an inverse
gaussian distribution.
How can I obtain best estimation for the two parameters of inverse
gaussian based on my data?
Thanks. |
|
h******3
发帖数: 190 | 23 Bayesian hierarchical model里通常用inverse wishart作为covariance matrix的
conjugate prior. 我的问题是怎么选择inverse wishart的scale matrix. 通常就用
identity matrix吗? 对estimates有什么影响. 多谢. |
|
T*********r
发帖数: 11175 | 24 【 以下文字转载自 Fitness 讨论区 】
发信人: TechniColor (坚决服从rourou的领导), 信区: Fitness
标 题: 有用Inversion Table的吗？
发信站: BBS 未名空间站 (Sat Mar 22 23:57:04 2014, 美东)
最近腰椎间盘突出越发严重了，有朋友推荐用Inversion Table
想问问大家有没有经验？
特别是要不要在腰那垫枕头
有些机器是有的，有些是没有的？
另外，这种倒立姿势，会不会让血液突然都流到头部，有什么问题吗？
我腰病后确实发了耳石症，不过自己会耳石复位，问题倒不大，只是比较难受 |
|
G*******s
发帖数: 10605 | 25 【 以下文字转载自 SmartShopper 俱乐部 】
发信人: GoRockets (火箭加油), 信区: SmartShopper
标 题: Body Flex Gravity Inversion System $86
发信站: BBS 未名空间站 (Fri Apr 27 20:26:53 2012, 美东)
Sears has Body Flex IT9910 Gravity Inversion System for $99.99. Add a filler
to reach $100 and apply code LAST2DAYS. Price would be $85.88 with free in-
store pickup. Amazon has it for $199.99.
http://userquote.com/forum/index.php?topic=1244.msg1516#msg1516 |
|
z****i
发帖数: 245 | 26 在Operating.Systems.Design.and.Implementation书上， 2.2.4 有一段话
Consider a computer with two processes, H, with high priority and L, with
low priority, which share a critical region. The scheduling rules are such
that H is run whenever it is in ready state. At a certain moment, with L in
its critical region, H becomes ready to run (e.g., an I/O operation
completes). H now begins busy waiting, but since L is never scheduled while
H is running, L never gets the chance to leave its critical region, so H... 阅读全帖 |
|
l******d
发帖数: 530 | 27 这书上讲的情况不大对“H now begins busy waiting”，H不一定是busy waiting，跟
os实现有关。大多数priority inversion的概念都是有3个priority level的，low
priority得到high priority想要的resource，但是一直被其它medium priority的抢占。
btw，这是啥方向的面试题，感觉像是real－time system的 |
|
l******d
发帖数: 530 | 28 我猜Andrew S Tanenbaum在教科书里是为了简化用了2个process的情况。在real-time
community里priority inversion基本都是3个不同priority的process才出现的。
你是real-time方向的？这个方向的专业不是基本都要us citizenship吗 |
|
i*****y
发帖数: 3449 | 29 这些所谓的LEVERAGED ETF都是BORN LOSER，INVERSE的更是如此，波动个几下子，就跌
的差不多了，大牛们以为如何。 |
|
j********d
发帖数: 157 | 30 SBM/SWN(2x) are trading at very thin volume (<100K per day).
Is there any other inverse ETF of basic material sector with more decent
volume (>0.5 M, ideally >1M)? |
|
k****s
发帖数: 95 | 31 高处污染小，因为inversion是污染在下面，热空气在上面，空气不流通。很多人直接
去山上度假。
这是我在city data上面看到的，没有亲身经历。 |
|
L**********n
发帖数: 813 | 32 普通青年说:第二张空气真好。
文艺青年说:还是第一张高端大气上档次有韵味，如人间仙境。
小资青年说:inversion的时候得请病假去山上躲躲
二逼青年说:盐湖城的地上果然好多盐哦。
照片版权所有: 小资青年 |
|
i***e
发帖数: 3219 | 33 第一张其实不严重。
inversion的时候确实是上山滑雪的好时机。 |
|
b*********r
发帖数: 114 | 34 本人腰椎间盘突出，年龄44。
我只能骑车和游泳。
买了一个inversion table, 想知道一些做这个运动的注意事项。
比如，一次倒立多长时间？
倒立时可不可以做仰卧起坐？
一组做多少次？
一天做多少组？
希望有经验的朋友给些建议，不胜感激！ |
|
b*********r
发帖数: 114 | 35 多谢回复,但是还没有inversion table方面的建议.自己顶一下.
另,NNNOOO, 很多运动不能做, 但骑车很好,增强腿,臀,腰腹肌肉,并且,运动是不会痛. |
|
a***e
发帖数: 575 | 36 From my inversion table user guide: 5-10 mins each time, in the morning and
evening. Warm up first.
-- You probably should read your user guide, too.
You can twist on the table but don't do 仰卧起坐 since it will swing back (
unless your table can be locked in place). |
|
g***l
发帖数: 18555 | 37 5节都脱出，那不成了畸形了吗？大家都突出了，就不叫突出了。inversion table也就
是缓解一下挤压的DISC吧，突出的，TABLE也不会帮你按回去，倒挂也就几分钟，搞不
好还不如趴床上休息半小时。 |
|
T*********r
发帖数: 11175 | 38 最近腰椎间盘突出越发严重了，有朋友推荐用Inversion Table
想问问大家有没有经验？
特别是要不要在腰那垫枕头
有些机器是有的，有些是没有的？
另外，这种倒立姿势，会不会让血液突然都流到头部，有什么问题吗？
我腰病后确实发了耳石症，不过自己会耳石复位，问题倒不大，只是比较难受 |
|
mw
发帖数: 525 | 39 ....
googled for 2 hours but not yet found any free code to inverse a matrix....
can anyone here suggest a URL? thanks a billion!!!! |
|
b***y
发帖数: 2799 | 40 ☆─────────────────────────────────────☆
slipper (ohh) 于 (Thu Oct 13 20:16:21 2005) 提到:
anybody know if VC++ has a function , which take a random number as input (the
random number is between 0 and 1), and it use inverse method to output a
value, which follow normal distri.? or dose VC has normal distribution random
number generator? Thanks.
☆─────────────────────────────────────☆
fightwater (QT) 于 (Fri Oct 14 12:53:06 2005) 提到:
using box-muller algorithm
http://en.wikipedia.org/wiki/Bo |
|
k******n
发帖数: 35 | 41 我用的是kile(1.9)＋kdvi，但是kdvi里面的inverse search不工作。双击kdvi的页面
没有任何反应。我已经在Settings->Configure Kdvi->DVI specials里面把kile设置为
editor了，为什么？请大家赐教。谢谢！ |
|
L****r
发帖数: 33 | 42 【 以下文字转载自 Programming 讨论区 】
【 原文由 Lisper 所发表 】
can we write a inverse-compiler which reads in source code in
assembly language, and generate source code in HLL.
advantages:
1. deal with portability problem of assembly code.
2. TAOCP by knuth was written in MIX, if you have a MIX->C compiler,
then we can read TAOCP in C... |
|
z****c
发帖数: 6 | 43 A is N by M? Please check your problem and make sure if A is square or not.
Note only square matrix has inverse matrix. And obviously, you can not
solve M unknowns from N equations. |
|
F****r
发帖数: 34 | 44 yes, the matrix is not square
just want to get the least aquare solution.
We already can got the result.
The problem is just time.
now we use the coarse grid, for one iteration it take about 1 day.
usually after 4 or 5 iteration we can see something in the result.
this is just the test version.
we need to try finer grids, it means larger matric inverse.
it may take a few days for iteration fineshed.
that is why we need to find the parallel library.
then we can use multiple processors to do this |
|
F****r
发帖数: 34 | 45 well, in my problem, we use the least square solution.
the iteration I said is not just finished one matrax inverse.
It is the program fineshed and get result.
like you said, our program need about a thousand iterations
to converge.
we need to use the new ouput as input.
run severals times.
There should be something designed to solve this problem.
this is very common in tomography. |
|
s*****t
发帖数: 1994 | 46 OK, what I used is exactly LSQR, and the problem what
I solve is exactly tomography.
Say, for one iteration, what I meant is one
A*x and then A^T * y, where ^T means transpose,
and y is the result from the previous iteration.
You know, if you want to speed up your code, it is
to speed up matrix multiplication A*x, and same way
A^T * y. The LSQR itself is not very time-consuming.
If you did not use LSQR, or other inversion code,
I believe your problem remains same, to speed up
matrix multiplicati |
|
m*******r
发帖数: 3635 | 47 请教各位大虾，
有没有软件数据包可以计算Numerical Laplace Inversion啊？
就是说原函数也都是Numerical的,没有Analytical的形式
非常感谢！ |
|
s***t
发帖数: 195 | 48 get a 64-bit system. but if you use the dense matrix method, it will
take a long long time.
and usually you shouldn't use the inverse directly. do a qr or svd
instead.
'.
free |
|
c****n
发帖数: 21367 | 49 well... just program it in C and allocate the memory by yourself
(if you really want the inverse, but it is really a rare request)
20k x 20k is not too bad, i had done same order not-so-sparse matrix
operations on single work station with 4G ram, highly time consuming
but feasible. you really need a SCSI HDD to cache the intermidiate
results.
the final accuracy is in doubt so you might need to store partial
operation procedures and evaluate them at the finalization procedure
also do take notes o |
|
c****n
发帖数: 21367 | 50 wooops, it is sparse... 20k x 20k sparse is really not too bad
however, for sparse matrix inversion, the first of the first is to
check whether there is empty row/column...
try "help sparse" in matlab...
.. |
|
