Blog Archives

Registration closing for UseR! 2011

July 18, 2011
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Registration closing for UseR! 2011

Friday July 22 is the last day on which you can register for UseR! 2011 at the University of Warwick.  The conference will be 2011 August 16-18. You can peruse the book of abstracts and view the draft schedule. I am scheduled to give a talk on “Random input testing with R”.  The abstract is: … Continue reading...

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On “Stock correlation has been rising”

July 17, 2011
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On “Stock correlation has been rising”

Ticker Sense posted about the mean correlation of the S&P 500. The plot there — similar to Figure 1 — shows that correlation has been on the rise after a low in February. Figure 1: Mean 50-day rolling correlation of S&P 500 constituents to the index. For me, this post raised a whole lot more … Continue reading...

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Testing an S&P 500 prediction

July 10, 2011
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Testing an S&P 500 prediction

If a particular prediction comes true, how surprised should we be? The prediction The page that sparked my curiosity tells of a prediction made a year ago that the S&P 500 would beat its historic high by the end of 2011.  It says that at the point the prediction was made, the level of the … Continue reading...

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Winsorization

June 30, 2011
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Winsorization

Winsorization replaces extreme data values with less extreme values. But why Extreme values sometimes have a big effect on statistical operations.  That effect is not necessarily a good effect.  One approach to the problem is to change the statistical operation — this is the field of robust statistics. An alternative solution is to just change … Continue reading...

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Talking The R Journal latest release

June 24, 2011
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Talking The R Journal latest release

Volume 3/1 of The R Journal has been released. It of course has articles about using R.  In addition it has a feature that I highly support.  In preparation for the UseR! Conference 2011 August 16-18 in Coventry there are two Help Desk articles on making a good technical presentation. Technical presentation Rob Hyndman writes … Continue reading...

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Performance ratios, bootstrapping and infinite variances

June 18, 2011
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Performance ratios, bootstrapping and infinite variances

If returns had infinite variance, would there be a problem bootstrapping information ratios? Background There is a discussion on the Quant Finance group of LinkedIn with the title: “How do you measure the confidence intervals of performance ratios?” One suggestion was to use the statistical bootstrap. This resulted in a discussion of the efficacy of … Continue reading...

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Market arrows

June 16, 2011
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Market arrows

Graphs like Figure 1 are reasonably common.  But they are not reasonable. Figure 1: A (log) price series with an explicit guide line. Some have the prices on a logarithmic scale, which is an improvement on the raw prices. The problem with this sort of plot is that two particular data points are taken as … Continue reading...

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Selections from the R/Finance conference

June 2, 2011
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Selections from the R/Finance conference

The R/Finance conference happened in Chicago at the end of April.  If, like me, you weren’t there, you can still benefit from it because slides from many of the talks are now online. Here is a quick synopsis (in chronological order) of some of the talks I found most interesting. Michael Kane Michael Kane and … Continue reading...

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Specific differences between Ledoit-Wolf and factor models

May 22, 2011
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Specific differences between Ledoit-Wolf and factor models

What can we learn about the difference in structure between a Ledoit-Wolf variance matrix and a corresponding factor model variance? Previously We’ve generated a set of random portfolios with constraints on the risk fractions of a Ledoit-Wolf variance matrix, and a corresponding set of random portfolios with risk fraction constraints from a statistical factor model. … Continue reading...

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Again with Ledoit-Wolf and factor models

May 4, 2011
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Again with Ledoit-Wolf and factor models

We come closer to a definitive answer on the relative merit of Ledoit-Wolf shrinkage versus a statistical factor model for variance matrices. Previously This post builds on the post entitled: A test of Ledoit-Wolf versus a factor model That post depended on some posts previous to it. New information Previously we generated random portfolios with … Continue reading...

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