j*****h
发帖数: 2577 | 1 关于Gamma的学习笔记。欢迎参观、指导。。
1. 在哪见过、听说过Gamma？
2. 什么是Gamma？
2.1. 显示器Gamma曲线
2.2. 检查显示系统的Gamma值
3. 什么是Gamma校正？
4. Gamma校正可能发生在哪里
4.1. 系统级（硬件、操作系统）
4.2. 应用程序级
4.3. 文件级
5. 改变Gamma带来的影响
5.1. 影调的变化
5.2. 颜色的变化
5.3. 其它
6. 校正Gamma的理由
6.1. 标准化及互换性
6.2. 算法上的要求
7. 不校正Gamma的理由
7.1. 现实的非标准化
7.2. 更符合视觉特性
7.3. 可能导致颜色数的减少
8. 结论
1. 在哪见过、听说过Gamma？
* 还用说，Adobe Gamma
* 常听说MAC的默认Gamma是1.8，PC的是2.2
* 我的显卡驱动程序里有Gamma调节
* 我下载了一个软件，也可以调节显示器的Gamma
* WinDVD播放器带Gamma校正功能
* ACDSEE的曝光调节里可以调Gamma
* ACDSEE的选项中有Enable Gamma Correction |
|
s*****t
发帖数: 1994 | 2 GAMMA射线爆发(GAMMA-Ray Burst，简称GAMMA爆)是宇宙中已知威力最大的爆炸，也是现
代天文学中最神秘的现象之一。
GAMMA射线就是高能量光子。天文学家发现几乎每天都发生几次GAMMA爆引起的强烈的GA
MMA射线束穿越我们的天空，其持续时间一般只有几十毫秒到一分钟，但强度高得惊人，
一次GAMM A爆释放的总能量超过太阳100亿年所释放出的全部能量。
几十年来有关GAMMA爆的观测结果表明，GAMMA爆随机地均匀地发生在我们的宇宙中。天
文学家原来认为GAMMA爆只发生在离我们非常遥远的地方，但是最近一位美国航空航天局
(NASA)戈达尔德(GODDARD)航天飞行中心的科学家杰· 诺里斯 (Jay Norris)却发现了1
00个比较“近 ”的GAMMA爆--距离我们地球不到三亿两千五百万光年。
杰· 诺里斯是在分析了1，400组GAMMA爆数据后得到这一结果的，这些GAMMA爆距离我们
地球之近和数目之可观，大大出乎科学家们的预料。
最近一个由皮罗(Luigi Piro)博士领导的研究小组指出，一些GAMMA爆似乎来自于新星体
产生的区域。他们在分析来自美国 |
|
s*****t
发帖数: 1994 | 3 GAMMA射线爆发(GAMMA-Ray Burst，简称GAMMA爆)是宇宙中已知威力最大的爆炸，也是现
代天文学中最神秘的现象之一。
GAMMA射线就是高能量光子。天文学家发现几乎每天都发生几次GAMMA爆引起的强烈的GA
MMA射线束穿越我们的天空，其持续时间一般只有几十毫秒到一分钟，但强度高得惊人，
一次GAMM A爆释放的总能量超过太阳100亿年所释放出的全部能量。
几十年来有关GAMMA爆的观测结果表明，GAMMA爆随机地均匀地发生在我们的宇宙中。天
文学家原来认为GAMMA爆只发生在离我们非常遥远的地方，但是最近一位美国航空航天局
(NASA)戈达尔德(GODDARD)航天飞行中心的科学家杰· 诺里斯 (Jay Norris)却发现了1
00个比较“近 ”的GAMMA爆--距离我们地球不到三亿两千五百万光年。
杰· 诺里斯是在分析了1，400组GAMMA爆数据后得到这一结果的，这些GAMMA爆距离我们
地球之近和数目之可观，大大出乎科学家们的预料。
最近一个由皮罗(Luigi Piro)博士领导的研究小组指出，一些GAMMA爆似乎来自于新星体
产生的区域。他们在分析来自美国 |
|
y*****w
发帖数: 1350 | 4 各位distribution大拿好，我最近有个sample size calculation project。是count
data，具体说是number of patient visits, with number of episodes for each
number of visit。请各位帮着参谋看一下我做的是否合适，给些意见。
Sample data如下：
# patient visit episode
---------------------------------
1 156
2 287
3 589
4 899
5 1535
6 1408
7 1017
8 ... 阅读全帖 |
|
c****t
发帖数: 19049 | 5 Gamma / Pure (25.00-34.75 HZ) / 30 Minutes / Gamma is associated with
information-rich task processing and high-level information processing "A
New Theory of Consciousness" For scientists who study the human brain, even
its simplest act of perception is an event of astonishing intricacy. Gamma
brain activity may be a kind of binding mechanism. Gamma waves serve to
connect structures in the cortex where advanced information processing
occurs, and the thalamus, a lower brain region where complex r... 阅读全帖 |
|
m******t
发帖数: 273 | 6 【 以下文字转载自 Statistics 讨论区 】
发信人: myregmit (myregmit), 信区: Statistics
标 题: long time generating gamma distribution in python
发信站: BBS 未名空间站 (Thu Mar 13 19:04:24 2014, 美东)
I need to generate a truncated gamma distribution pdf curve and histogram in
python 3.
2 on win7.
import numpy as np
import matplotlib.pyplot as plt
import scipy.special as sps
shape, scale = 2., 2. # mean and dispersion
counter =0
s = []
upper_bound = 4
lower_bound = 0.5
while (counter <= 1000):
t = np.random.gamma(shape, ... 阅读全帖 |
|
m******t
发帖数: 273 | 7 【 以下文字转载自 Statistics 讨论区 】
发信人: myregmit (myregmit), 信区: Statistics
标 题: long time generating gamma distribution in python
发信站: BBS 未名空间站 (Thu Mar 13 19:04:24 2014, 美东)
I need to generate a truncated gamma distribution pdf curve and histogram in
python 3.
2 on win7.
import numpy as np
import matplotlib.pyplot as plt
import scipy.special as sps
shape, scale = 2., 2. # mean and dispersion
counter =0
s = []
upper_bound = 4
lower_bound = 0.5
while (counter <= 1000):
t = np.random.gamma(shape, ... 阅读全帖 |
|
g****t
发帖数: 31659 | 8 gamma 分布的公式网上一查就能看到。
里头就gamma函数是个积分，别的都是加减乘除。
gamma函数那个积分的计算有专有的算法，
不过需要花时间看文献。numerical receipts啥的
应该有现成的代码。
如果你不想查文献，gamma函数按它的级数极限定义
算算看能不能满足你得计算速度要求。
distribution
the |
|
w*******y
发帖数: 60932 | 9 Link:
http://www.amazon.com/GAMMA-Classic-Interior-Chassis-Black/dp/B
GAMMA Classic Series ATX Mid Tower Interior Steel Chassis
Product Features
* 6 fan capability ( one rear 120mm included )
* Black Interior
* Wire routing: motherboard punched holes allows for quick CPU bracket
removable and optimal wire routing, turned HDD also helps with managing
cables
* High end graphics card support, the Gamma features space that is
especially designed to fit longer 10.5-Inch cards
Technica... 阅读全帖 |
|
c*********e
发帖数: 774 | 10 Alpha++ world cities: London, New York
Alpha+ world cities: Hong Kong, Paris, Singapore, Tokyo, Shanghai, Dubai,
Sydney, Beijing
Alpha world cities: Milan, Toronto, Sao Paulo, Madrid, Chicago, Mumbai, Los
Angeles, Moscow, Frankfurt, Mexico City, Amsterdam, Kuala Lumpur, Brussels
Alpha− world cities: Miami, Seoul, Dublin, Jakarta, Melbourne, Buenos
Aires, Zurich, New Delhi, Munich, Boston, Warsaw, Vienna, Atlanta, Barcelona
, Bangkok, Istanbul, Taipei, Johannesberg, Washington, San Francisc... 阅读全帖 |
|
m******t
发帖数: 273 | 11 【 以下文字转载自 Quant 讨论区 】
发信人: myregmit (myregmit), 信区: Quant
标 题: error of gamma.fit() in python
发信站: BBS 未名空间站 (Sat Mar 15 11:30:18 2014, 美东)
in Python 3.2, I need to find gamma fit for data.
param = gamma.fit(samp) // samp is a list of double
I got error: TypeError: cannot perform reduce with flexible type
Any help wouldbe appreciated.
best |
|
s******o
发帖数: 298 | 12 Scientists believe they have solved a 35-year-old mystery surrounding the
origin of gamma-ray bursts.
by Vanessa Thomas
Since the first gamma-ray burst was spotted by government satellites in 1967,
scientists have puzzled over the cause of these fleeting but incredibly
powerful phenomena. Their befuddlement may now be over. A space telescope has
found clues in the afterglow of a distant gamma-ray burst that point to
supernovae as the producers of the universe's most violent events.
Astronomers h |
|
s*****t
发帖数: 1994 | 13 HESS Gamma-Ray Telescope
Credit: The HESS Collaboration
Explanation: Most ground-based telescopes with lenses and mirrors are hindered by the
Earth's nurturing, protective atmosphere that blurs images and scatters and absorbs light.
But this telescope was designed to detect extreme gamma rays - photons with over 100 billion
times the energy of visible light - and actually requires the atmosphere to operate. As the
gamma rays impact the upper atmosphere they produce air shower |
|
s*****t
发帖数: 1994 | 14 A Gamma Ray Burst - Supernova Connection
Credit: Al Kelly (JSCAS/NASA) & Arne Henden (Flagstaff/USNO)
Explanation: New evidence has emerged that a mysterious type of explosion known as a
gamma ray burst is indeed connected to a supernova of the type visible in the above image.
Two weeks ago, the orbiting HETE satellite detected gamma-ray burst GRB030329. The
extremely bright burst was found hours later to have an extremely bright afterglow in visible
light, and soon set the record for th |
|
B********e
发帖数: 10014 | 15 oracle里果然没有这个东西，甚至连gamma函数都没有，只能提供一点建议
1. 写出你的公式，问题应该只出在gamma函数，如果gamma的参数是整数就没问题，自己
随便写一个factorial函数了。如果不是整数需要一个积分code随便搜一个也不难。其他
指数函数幂函数oracle都有。
2.写一个c，或c++,或用cbuilder，或者delphi程序，调用
3.数据接口connect excel调用。（我们那时候只用odbc或者pb的接口，现在应该日新月
异了）
4.发个email给oracle技术支持，我们经常干，有时候很傻嘿嘿 |
|
b*******g
发帖数: 513 | 16 Gamma(0)好象invalid？对于一个正整数n应该有gamma（n）=n！，那么gamma（0）是多
少呢？多谢。 |
|
s**e
发帖数: 1834 | 17 It is Gamma(n+1) = n! and Gamma(x+1)=x*Gamma(x).
So x=0 is a pole of G(x), so is x= -1, -2, ... |
|
g**********t
发帖数: 475 | 18 貌似Gamma分布非常的常见啊，在各种地方都能见到。为什么Gamma分布这么powerful？
Poisson分布很常见是因为很多随即过程都是poisson过程。那有什么内在的原因导致
Gamma分布如此常见呢？ |
|
s********7
发帖数: 52 | 19 Very good question
First of all, vega and gamma are completely 2 different things. why? Notice
that gamma is a market risk parameter while vega measures model risk. Put in
other words, when market(stock price) moves around, convexity(gamma) can be
captured by the realized volatility. when the implied vol(BlackSholes model
input) fluctuates, vega is realized.
Second of all, consider an option that's close to ATM but not exactly( what
the case will be at most of the time)
vega grows larger as time |
|
x*********8
发帖数: 36 | 20 Isn't there a linkage between Gamma and Vega?
Gamma brings the same effect as Vega in short term.
Vega really needs be bucketed, by term and by moneyness.
Personally I think Gamma is more risk because short-term squeeze often
happens if you over-leveraged, which may not be the case in the question
been asked.
depends
volitility." |
|
z*********o
发帖数: 541 | 21 能不能帮忙解释一下gamma function 和 the pdf of gamma distribution的之间关系
？ |
|
b*******g
发帖数: 513 | 22 Gamma(0)好象invalid？对于一个正整数n应该有gamma（n）=n！，那么gamma（0）是多
少呢？多谢。 |
|
c****s
发帖数: 63 | 23 我的问题是：
我现在有cost为outcome的数据，要用gamma distribution来fit,
但是难题是predictors有1000个,所以又要同时选择predictor.
我的想法:
1.如果用stepwise方法来选，就可以既fit gamma 又同时select variables. 在R中可
以实现，但老板所stepwise不好，让用lasso来select variables.
2.如果直接先用lasso选变量，再去fit model，好像也不太对。因为lasso fit的
是least Angle regression, 不是基于gamma distribution. 应该不能适用于cost
data.
不知道大家遇到这种问题该怎么办，SAS, Stata or R, 那个能解决这个问题呢？
或者有什么好的建议，先谢谢了！ |
|
y*****w
发帖数: 1350 | 24 Actually the intercept in the ODS output is the estimated log mean of the
fitted gamma distribution, so I don't need the output statement in PROC
GENMOD. The pertinent code becomes:
proc genmod data=mydata;
model visit = / dist=gamma link=log;
freq episode;
ods output parameterestimates=pe;
run;
proc transpose data=pe out=tpe;
var estimate;
id parameter;
run;
data _null_;
set tpe;
call symputx("logmean", intercept);
call symputx("scale", scale);
stop;
run;
data pmf;
do t = 1 ... 阅读全帖 |
|
m******t
发帖数: 273 | 25 I need to generate a truncated gamma distribution pdf curve and histogram in
python 3.2 on win7.
The following program is correct ?
import numpy as np
import matplotlib.pyplot as plt
import scipy.special as sps
shape, scale = 2., 2. # mean and dispersion
counter =0
s = []
upper_bound = 4
lower_bound = 0.5
while (counter <= 1000):
t = np.random.gamma(shape, scale)
if (lower_bound <= t <= upper_bound) :
s.append(t)
counter += 1
count, bins, ignored = plt.hist(s, 50, normed... 阅读全帖 |
|
m******t
发帖数: 273 | 26 【 以下文字转载自 Quant 讨论区 】
发信人: myregmit (myregmit), 信区: Quant
标 题: error of gamma.fit() in python
发信站: BBS 未名空间站 (Sat Mar 15 11:30:18 2014, 美东)
in Python 3.2, I need to find gamma fit for data.
param = gamma.fit(samp) // samp is a list of double
I got error: TypeError: cannot perform reduce with flexible type
Any help wouldbe appreciated.
best |
|
l*****e
发帖数: 890 | 27 我的想法是用proc fcmp 定义了CDF 和 PDF是不是就足够了呢？还是需要再定义下
moment estimation？以下是我的code：
proc fcmp library=sashelp.svrtdist outlib=work.sevexmpl.models;
function KumGG_pdf(x,lambda,phi,k, tau, alpha);
dx=x/alpha;
zx=dx**tau;
m=tau*k-1;
igammar=cdf("gamma",zx,k,1);
term1=(lambda*phi*tau)/(alpha*gamma(k));
return (term1*(dx**m)*exp(-zx)*(igammar**(lambda-1))*((1-igammar**
lambda)**(phi-1)));
endsub;
function KumGG_cdf(x,lambda,phi,k, tau, alpha);
dx=x/alpha;
zx=dx**tau;... 阅读全帖 |
|
s******o
发帖数: 298 | 28 Scientists believe they have solved a 35-year-old mystery surrounding the
origin of gamma-ray bursts.
by Vanessa Thomas
Since the first gamma-ray burst was spotted by government satellites in 1967,
scientists have puzzled over the cause of these fleeting but incredibly
powerful phenomena. Their befuddlement may now be over. A space telescope has
found clues in the afterglow of a distant gamma-ray burst that point to
supernovae as the producers of the universe's most violent events.
Astronomers h |
|
s*****t
发帖数: 1994 | 29 HESS Gamma-Ray Telescope
Credit: The HESS Collaboration
Explanation: Most ground-based telescopes with lenses and mirrors are hindered by the
Earth's nurturing, protective atmosphere that blurs images and scatters and absorbs light.
But this telescope was designed to detect extreme gamma rays - photons with over 100 billion
times the energy of visible light - and actually requires the atmosphere to operate. As the
gamma rays impact the upper atmosphere they produce air shower |
|
s*****t
发帖数: 1994 | 30 A Gamma Ray Burst - Supernova Connection
Credit: Al Kelly (JSCAS/NASA) & Arne Henden (Flagstaff/USNO)
Explanation: New evidence has emerged that a mysterious type of explosion known as a
gamma ray burst is indeed connected to a supernova of the type visible in the above image.
Two weeks ago, the orbiting HETE satellite detected gamma-ray burst GRB030329. The
extremely bright burst was found hours later to have an extremely bright afterglow in visible
light, and soon set the record for th |
|
k*****a
发帖数: 823 | 31 国产的gamma mx具体有什么问题？偶那件06年国产的sigma sv看上去挺好的啊，做工和
另一件06年canada产的gamma sv没太多区别。 |
|
n****u
发帖数: 173 | 32 第一次来这个版，不知能不能在这里发帖卖东西.. 如违反版规，很抱歉~ 同时也请好
心人推荐可以卖这类物品的网站论坛~多谢！
现有一件始祖鸟 Arc'teryx Gamma Mx Softshell 转让出售，卖价200刀包邮，黑色，
女款，S号。全新带牌正品，购于backcountry.com。
防风，防泼溅水，超轻，荣获多项户外大奖，是软壳中的精品。如果你是户外爱好者或
者打算送朋友，这件软壳必是最佳选择之一。
详细介绍请见官网:http://www.arcteryx.com/Product. ... l=Gamma-MX-Jacket-W
原价299刀，backcountry.com售239刀。
如有兴趣的朋友，欢迎联系 |
|
n******r
发帖数: 1247 | 33 I have used both many times.
Both ones are solid that will last forever.
Every parts of klippermate looks cheap including the two metal clamps.
However, they don't slip and are 100 times better than gamma's plastic
clamps. When pulling, it's easier to adjust the string length with
Klippermate too.
Besides, klippermate has stops for the turning plate and can be used to
string Prince O3 racquets without extra tools. X2 can't.
Gamma looks better, klippermate works better. |
|
z********i
发帖数: 610 | 34 最近在细胞里面做了几次gamma tubulin staining，用了不同的固定方法，甲醇固定后
centriole 信号很强，细胞核中gamma-tubulin信号很弱，细胞质中的信号强一些。看
文献好像是这样。
但是换成PFA固定后centriole信号比较弱，还是能看到了。奇怪的是细胞核中的信号强
一些。到底哪一个染色的结果真实一些？
我还共染了另一个蛋白，带FLAG tag不同的固定方法，得到的结果也不一样。多谢！ |
|
r***r
发帖数: 123 | 35 BlackKnife,
Thanks for your expertise.
I know very little about statistics. Don't even know what is gamma distribution
. Would you please give me some formula or agrithom to calculate gamma
inverse. I couldn't find any.
We currently use Excel/SAS to get around of this. My boss want do it in the
Oracle.
Thanks once again!
自己
其他
新月 |
|
z****e
发帖数: 702 | 36 假设有一组独立同分布的gamma(a,b),这个组的变量个数是Poisson分布Poi(N),
那么这些变量的和是gamma(aN,b)么？thx |
|
|
a*s
发帖数: 10 | 38 Not sure if your example is correct. In option market making, buying gamma
typically means buying short dated options, and you expect the underlying
will move a lot. Hence, via delta hedging, you'll buy low and sell high. If
you don't do delta hedging, I'm not sure what buying gamma mean. |
|
b**********5
发帖数: 51 | 39 业界是如何实现 Gamma Trading 和 Vega Trading 的啊？什么时候该 Trade Gamma 和
什么时候
Trade Vega ？头寸建立后，trader 每天要做些什么？例如要不要每天 adjust 头寸和
算 Greeks
之类的？想了解一下业界是如何做的。谢谢。 |
|
EM
发帖数: 715 | 40 good thoughts. but I think gamma belongs to the model risk since 0.5*gamma*
imp_vol^2*dt is almost equivalent to the theta decay |
|
i****k
发帖数: 39 | 41 Q1: Assuming Black-Scholes and given our portfolio is now Vega neutral, will
it be Gamma neutral?
Q2: If we don't believe in Black-Scholes will our portfolio be Gamma neutral
if it is Vega neutral? |
|
l*********t
发帖数: 89 | 42 题目：
Given a long option position with 2 years to expiry, what do I care more
about and why? Gamma or Vega?
我找了下各方文献，终于在Hull的书上17.8节末尾找到一句话，Quote:" Whether it
is best to use an available traded option for vega or gamma hedging depends
on the time between hedge rebalancing and the volatility of the volitility."
Hull关于这句话还有个注释：让参见《Hedging the Risks from Writing Foreign
Currency Options》 Hull 1987. 我在sciencedirect数据库里搜到了，不过没权限看
不了。
我感觉这道题没那么复杂，怎么让Hull一说就变得比较复杂了呢？
请各路高手予以指教，不一定非要用Hull的理论。如果要用的话，哪位大侠... 阅读全帖 |
|
c****y
发帖数: 3592 | 43 我明白用calendar spread就可以做，但是意义何在？
如果说long gamma/short vega是expect market move but vol stay low那还可以解释
，但是反过来既然long vega肯定是市场波动得很厉害为何还要short gamma |
|
h****q
发帖数: 42 | 44 Can anyone recommend me some books about Gamma Scalping? I was wondering how
to find the optimal level for the gamma scalping. Thank you very much. |
|
m******t
发帖数: 273 | 45 in Python 3.2, I need to find gamma fit for data.
param = gamma.fit(samp) // samp is a list of double
I got error: TypeError: cannot perform reduce with flexible type
Any help wouldbe appreciated.
best |
|
d***p
发帖数: 306 | 46 【 以下文字转载自 Chemistry 讨论区 】
发信人: ddppp (er'do's耳朵屎), 信区: Chemistry
标 题: 修改图片的gamma值在允许范围么？
发信站: BBS 未名空间站 (Tue Sep 19 12:43:46 2006)
背景信号比较多，本来是调对比的，但仍然能模糊看见背景，发现调gamma从50到40就
比较有效，图片主要是看颜色，这样算不算伪造？ |
|
r***r
发帖数: 123 | 47 Please help me out of this.
I need a algorithm to write a function in ORACLE.
I know there is a function GammaInv in Excel and GamInv in SAS. Thoses
functions won't help me to implement it in Oracle.
I know very little about statistics. Don't even know what is gamma distribution
. Would you please give me some formula or agrithom to calculate gamma
inverse. I couldn't find any.
We are currently using Excel/SAS to get around of this. My boss want do it
in Oracle.
Thanks in advance! |
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z*******n
发帖数: 203 | 48 本人生物专业的，需要用gamma分布（概率密度函数）做一些计算，哪位能够给简单的
介绍一些相关的知识。1）函数公式中的各个参数的具体含义；2）有一些实验数据，如
何验证他们是否符合gamma分布；3）有哪一些软件可以做以上的计算和绘图。谢谢！ |
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c*****l
发帖数: 26 | 49 Gamma(0)没定义
另外，gamma（n）=(n-1)！不是n！ |
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s*********e
发帖数: 1051 | 50 i think it is ok to use lasso and here is why.
there are 2 parameters in gamma, scale and shape parameters. when shape
parameter is large, gamma converges to gaussian. so if you are working on
large sample, you should be fine. |
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