# Calculating Custom Fantasy Football Projections for Your League using R

**Fantasy Football Analytics in R**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)

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In prior posts, I have shown how to download fantasy football projections from ESPN, CBS, and NFL.com. In this post, I will demonstrate how to take the projected points from these sources and calculate the projected points for your custom league given your league settings. Calculating players’ projected points in your league will be important for picking the ideal team for your league.

## The R Script

The R script for calculating custom fantasy football projections for your league is located at:

https://github.com/dadrivr/FantasyFootballAnalyticsR/blob/master/R%20Scripts/Calculate%20League%20Projections.R

### League settings

In the first portion of the script, we define (and can modify) your league settings. Here are the settings for my fantasy league:

#Customize your league settings

passYdsMultiplier <- (1/25) #1 pt per 25 pass yds

passTdsMultiplier <- 4 #4 pts per pass td

passIntMultiplier <- -3 #-3 pts per INT

rushYdsMultiplier <- (1/10) #1 pt per 10 rush yds

rushTdsMultiplier <- 6 #6 pts per rush td

recYdsMultiplier <- (1/8) #1 pt per 8 rec yds

recTdsMultiplier <- 6 #6 pts per rec td

twoPtsMultiplier <- 2 #2 pts per 2-point conversion (not included in ESPN or CBS projections)

fumlMultiplier <- -3 #-3 pts per fumble lost (not included in ESPN projections)

### Calculating projected points for each source

We then take the projected stats for each of the categories above (e.g., passing yards, rushing yards) from each source and multiply them by the multiplier defined for your league above. Here are the calculations for ESPN’s projections:

projections$passYdsPts_espn <- projections$passYds_espn*passYdsMultiplier

projections$passTdsPts_espn <- projections$passTds_espn*passTdsMultiplier

projections$passIntPts_espn <- projections$passInt_espn*passIntMultiplier

projections$rushYdsPts_espn <- projections$rushYds_espn*rushYdsMultiplier

projections$rushTdsPts_espn <- projections$rushTds_espn*rushTdsMultiplier

projections$recYdsPts_espn <- projections$recYds_espn*recYdsMultiplier

projections$recTdsPts_espn <- projections$recTds_espn*recTdsMultiplier

projections$twoPts_espn <- projections$fumbles_espn*twoPtsMultiplier

projections$fumblesPts_espn <- projections$fumbles_espn*fumlMultiplier

The projected points for a given source is the linear (additive) combination of these point categories. For example, we add the projected points from each of the above categories for ESPN’s projections:

projections$projectedPts_espn <- rowSums(projections[,c("passYdsPts_espn","passTdsPts_espn","passIntPts_espn","rushYdsPts_espn","rushTdsPts_espn","recYdsPts_espn","recTdsPts_espn","twoPts_espn","fumblesPts_espn")], na.rm=T)

We complete each of these steps with the other sources (CBS and NFL.com). Once we have the projected points for each source, we have a couple options: 1) We can compute a simple average across the sites’ projections. 2) We can compute a weighted average where we weight the sources we trust more heavily in our average. 3) We can compute a latent variable that represents the common variance among the sources. I tend not to trust individual sources of projections because they tend not to reliably outperform the average, so I will compute an average and latent variable (but see here if you want an example of a weighted average of fantasy projections).

### Average across sources

To calculate an average of projections across sources, we first calculate an average of projected statistics for each of the categories across sources:

#Calculate average of categories

projections$passYds <- rowMeans(projections[,c("passYds_espn","passYds_cbs","passYds_nfl")], na.rm=TRUE)

projections$passTds <- rowMeans(projections[,c("passTds_espn","passTds_cbs","passTds_nfl")], na.rm=TRUE)

projections$passInt <- rowMeans(projections[,c("passInt_espn","passInt_cbs","passInt_nfl")], na.rm=TRUE)

projections$rushYds <- rowMeans(projections[,c("rushYds_espn","rushYds_cbs","rushYds_nfl")], na.rm=TRUE)

projections$rushTds <- rowMeans(projections[,c("rushTds_espn","rushTds_cbs","rushTds_nfl")], na.rm=TRUE)

projections$recYds <- rowMeans(projections[,c("recYds_espn","recYds_cbs","recYds_nfl")], na.rm=TRUE)

projections$recTds <- rowMeans(projections[,c("recTds_espn","recTds_cbs","recTds_nfl")], na.rm=TRUE)

projections$twoPts <- rowMeans(projections[,c("twoPts_espn","twoPts_cbs","twoPts_nfl")], na.rm=TRUE)

projections$fumbles <- rowMeans(projections[,c("fumbles_espn","fumbles_cbs","fumbles_nfl")], na.rm=TRUE)

Then we multiply the projected stats categories by the multiplier defined by our league settings:

#Calculate projected points for your league (avg of ESPN, CBS, and NFL projections)

projections$passYdsPts <- projections$passYds*passYdsMultiplier

projections$passTdsPts <- projections$passTds*passTdsMultiplier

projections$passIntPts <- projections$passInt*passIntMultiplier

projections$rushYdsPts <- projections$rushYds*rushYdsMultiplier

projections$rushTdsPts <- projections$rushTds*rushTdsMultiplier

projections$recYdsPts <- projections$recYds*recYdsMultiplier

projections$recTdsPts <- projections$recTds*recTdsMultiplier

projections$fumblesPts <- projections$fumbles*fumlMultiplier

The average projected points across sources is the sum of the points across categories (that have been averaged across sources):

### Latent variables

Latent variables are helpful for calculating an unobserved variable based on the common variance among various indicator variables. Latent variables tend to have stronger psychometric properties than simple average variables because they retain the common variance (thought to be “true” variance) and discard the unique variance (i.e., measurement error). Examination of the correlations among the various sources suggests that they are highly correlated (*r*s > .89), suggesting that they are measuring the same thing, and that they can be combined in a latent variable.

> round(cor(projections[,c("projectedPts_espn","projectedPts_cbs","projectedPts_nfl","projectedPts")], use="pairwise.complete.obs"),2)

projectedPts_espn projectedPts_cbs projectedPts_nfl projectedPts

projectedPts_espn 1.00 0.94 0.90 0.98

projectedPts_cbs 0.94 1.00 0.89 0.97

projectedPts_nfl 0.90 0.89 1.00 0.93

projectedPts 0.98 0.97 0.93 1.00

rescaleRange <- function(variable, minOutput, maxOutput){

minObserved <- min(variable)

maxObserved <- max(variable)

values <- (maxOutput-minOutput)/(maxObserved-minObserved)*(variable-maxObserved)+maxOutput

return(values)

}

#Rescale the factor scores to have the same range as the average projections data

projections$projectedPtsLatent <- as.vector(rescaleRange(variable=projectedPtsLatent, minOutput=0, maxOutput=max(projections$projectedPts)))

ggplot(densityData, aes(x=pointDensity, fill=sourceDensity)) + geom_density(alpha=.3) + xlab("Player's Projected Points") + ggtitle("Density Plot of Projected Points from 2012") + theme(legend.title=element_blank())

In my next post, I will compare the accuracy of last year’s projections from ESPN, CBS, and NFL.com, in addition to the accuracy of our average and latent variables.

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