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# Category Archives: Quant finance

## The look of verifying data

Get data that fit before you fit data. Why verify? Garbage in, garbage out. How to verify The example data used here is daily (adjusted) prices of stocks. By some magic that I’m yet to fathom, market data can be wondrously wrong even without the benefit of the possibility of transcription errors. It doesn’t seem … Continue reading

Posted in Quant finance, R language
Tagged data errors, data verification, missed stock split
9 Comments

## Introduction to stable distributions for finance

A few basics about the stable distribution. Previously “The distribution of financial returns made simple” satirized ideas about the statistical distribution of returns, including the stable distribution. Origin As “A tale of two returns” points out, the log return of a long period of time is the sum of the log returns of the shorter … Continue reading

Posted in Quant finance, R language
3 Comments

## The low volatility anomaly and CAPM

A look at a paper that explores possible assumption failures of CAPM that would explain the low volatility anomaly. Previously We’ve talked about CAPM before, in particular: 4 and a half myths about beta in finance There has also been substantial talk about low volatility investing. The paper The paper is “Explanations for the Volatility … Continue reading

## Implied alpha and minimum variance

Under the covers of strange bedfellows. Previously The idea of implied alpha was introduced in “Implied alpha — almost wordless”. In a comment to that post Jeff noticed that the optimal portfolio given for the example is ever so close to the minimum variance portfolio. That is because there is a problem with the example … Continue reading

Posted in Quant finance, R language
Tagged implied alpha, minimum variance portfolio, reverse optimization
7 Comments

## Variance matrix differences

Torturing portfolios to give different volatilities between a factor model and Ledoit-Wolf shrinkage. Previously There have been posts on: “What the hell is a variance matrix?” factor models Ledoit-Wolf shrinkage Question Two of the several ways to produce an estimate of the variance matrix of asset returns is a statistical factor model and Ledoit-Wolf shrinkage. … Continue reading

## The half variance approximation for mean returns

What’s that thing about arithmetic and geometric returns and the variance? Previously An introduction to the difference between simple and log returns is: A tale of two returns Issue Suppose you are predicting the mean annual return of an asset for some number of years. To simplify the discussion, let’s buy into the fantasy that … Continue reading

## Slouching towards simulating investment skill

When investment skill is simulated, it is often presented as if it is obvious how to do it. Maybe I’m wrong, but I don’t think it’s obvious. Previously In “Simple tests of predicted returns” we saw that prediction quality need not look like what you would find in a textbook. For example, there was a … Continue reading

## garch and the distribution of returns

Using garch to learn a little about the distribution of returns. Previously There are posts on garch — in particular: A practical introduction to garch modeling The components garch model in the rugarch package garch and long tails There has also been discussion of the distribution of returns, including a satire called “The distribution of … Continue reading

## Stock-picking opportunity and the ratio of variabilities

How good is the current opportunity to pick stocks relative to the past? Idea The more stocks act differently from each other relative to how volatile they are, the more opportunity there is to benefit by selecting stocks. This post looks at a particular way of investigating that idea. Data Daily (log) returns of 442 … Continue reading

Posted in Quant finance, R language
Tagged opportunity ratio, S&P 500, stock-picking opportunity, volatility
6 Comments

## A pictorial history of US large cap correlation

How has the distribution of correlations changed over the last several years? Previously Posts about correlation boxplots explained Data Daily returns of 443 large cap US stocks from 2004 through 2012 were used. The sample correlations — almost 98,000 of them — during each year were created. If we were actually using the correlations, then … Continue reading