# Simple Moving Average Strategy with a Volatility Filter: Follow-Up Part 1

April 23, 2012
By

(This article was first published on rbresearch » R, and kindly contributed to R-bloggers)

#### Analyzing transactions in quantstrat

This post will be part 1 of a follow up to the original post, Simple Moving Average Strategy with a Volatility Filter. In this follow up, I will take a closer look at the individual trades of each strategy. This may provide valuable information to explain the difference in performance of the SMA Strategy with a volatility filter and without a volatility filter.

Thankfully, the creators of the quantstrat package have made it very easy to view the transactions with a simple function and a single line of code.

getTxns(Portfolio, Symbol, Dates)

For the rest of the post, I will refer to the strategies as:

• Strategy 1 =  Simple Moving Average Strategy with a Volatility Filter
• Strategy 2 = Simple Moving Average Strategy without a Volatility Filter

It is evident from the equity curves in the last post that neither strategy did much from the year 2000 to 2012. For that reason, I will analyze the period from 1990 to 2000

Strategy 1 Transactions

                    Txn.Qty Txn.Price Txn.Fees  Txn.Value Txn.Avg.Cost Net.Txn.Realized.PL
1900-01-01 00:00:00       0      0.00        0       0.00         0.00                0.00
1992-10-23 00:00:00     410    414.10        0  169781.00       414.10                0.00
1994-04-08 00:00:00    -410    447.10        0 -183311.00       447.10            13530.00
1994-06-10 00:00:00     531    458.67        0  243553.77       458.67                0.00
1994-06-17 00:00:00    -531    458.45        0 -243436.95       458.45             -116.82
1995-05-19 00:00:00     247    519.19        0  128239.93       519.19                0.00
1998-09-04 00:00:00    -247    973.89        0 -240550.83       973.89           112310.90
1999-09-10 00:00:00      45   1351.66        0   60824.70      1351.66                0.00
1999-10-22 00:00:00     -45   1301.65        0  -58574.25      1301.65            -2250.45
1999-11-26 00:00:00      82   1416.62        0  116162.84      1416.62                0.00

Strategy 2 Transactions

                    Txn.Qty Txn.Price Txn.Fees  Txn.Value Txn.Avg.Cost Net.Txn.Realized.PL
1900-01-01 00:00:00       0      0.00        0       0.00         0.00                0.00
1992-10-23 00:00:00     410    414.10        0  169781.00       414.10                0.00
1994-04-08 00:00:00    -410    447.10        0 -183311.00       447.10            13530.00
1994-06-10 00:00:00     531    458.67        0  243553.77       458.67                0.00
1994-06-17 00:00:00    -531    458.45        0 -243436.95       458.45             -116.82
1994-08-19 00:00:00     593    463.68        0  274962.24       463.68                0.00
1994-09-30 00:00:00    -593    462.71        0 -274387.03       462.71             -575.21
1994-10-07 00:00:00     562    455.10        0  255766.20       455.10                0.00
1994-10-14 00:00:00    -562    469.10        0 -263634.20       469.10             7868.00
1994-10-21 00:00:00     560    464.89        0  260338.40       464.89                0.00
1994-12-02 00:00:00    -560    453.30        0 -253848.00       453.30            -6490.40
1995-01-13 00:00:00     548    465.97        0  255351.56       465.97                0.00
1998-09-04 00:00:00    -548    973.89        0 -533691.72       973.89           278340.16
1998-10-02 00:00:00      66   1002.60        0   66171.60      1002.60                0.00
1998-10-09 00:00:00     -66    984.39        0  -64969.74       984.39            -1201.86
1998-10-23 00:00:00      68   1070.67        0   72805.56      1070.67                0.00
1999-10-22 00:00:00     -68   1301.65        0  -88512.20      1301.65            15706.64
1999-10-29 00:00:00      70   1362.93        0   95405.10      1362.93                0.00

For ease of comparison, I exported the transactions for each strategy to excel and aligned the trades as close I could by date.

First, lets look at the trades highlighted by the red rectangle. Strategy 2 executed a trade for 548 units on 1/13/1995 and closed on 9/4/1998 for a total profit of $278340.16. By comparison, Strategy 1 executed a trade for 247 units on 5/19/1995 (about 4 months later) and closed on 9/4/1998 for a total profit of$112,310.90. This is a significant difference of $166,029. It is clear that this single trade is critical to the performance of the strategy. Now, lets look at the trade highlighted by the yellow rectangle. Both trades were closed on 10/22/1999. Strategy 1 resulted in a loss of$2,250.45 and Strategy 2 resulted in a gain of $15,706.64… a difference of$17,957.09.

The equity curve of Strategy 1 compared with Strategy 2 shows a clearer picture of the outperformance.

rbresearch

Why such a big difference?

For an even closer look, we will need to take a look at the measure of volatility we use as a filter. I will make a few modifications to the RB function so we can see the volatility measure and median.

#Function that calculates the n period standard deviation of close prices.
#This is used in place of ATR so that I can use only close prices.
SDEV <- function(x, n){
sdev <- runSD(x, n, sample = FALSE)
colnames(sdev) <- "SDEV"
reclass(sdev,x)
}

#Custom indicator function
RB <- function(x,n){
x <- x
roc <- ROC(x, n=1, type="discrete")
sd <- runSD(roc,n, sample= FALSE)
#sd[is.na(sd)] <- 0
med <- runMedian(sd,n)
#med[is.na(med)] <- 0
mavg <- SMA(x,n)
signal <- ifelse(sd < med & x > mavg,1,0)
colnames(signal) <- "RB"
ret <- cbind(x,roc,sd,med,mavg,signal)
colnames(ret) <- c("close","roc","sd","med","mavg","RB")
reclass(ret,x)
}

data <- cbind(RB(Ad(GSPC),n=52),SDEV(Ad(GSPC),n=52)) #RB is the volatility signal indicator and SDEV is used for position sizing
Created by Pretty R at inside-R.org
> data['1995']
close           roc          sd        med     mavg RB      SDEV
1995-01-13 00:00:00 465.97  0.0114830251 0.013545475 0.01088292 459.7775  0  8.924008
...
1995-05-19 00:00:00 519.19 -0.0121016078 0.012412166 0.01259515 472.6006  1 21.161032

The sd for 1995-01-13 is 0.0135 while the SDEV is 8.924. The sd for 1995-05-19 is 0.0124 while the SDEV is 21.16… the SDEV is almost 3 times larger even though our volatility measure is indicating a period of low volatility! (note: SDEV has a direct impact on position sizing)

Perhaps we should take a second look at our choice of volatility measure.

If you want to incorporate a volatility filter into your system, choose the volatility measure wisely…

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