multreg.R

nightlystats <- read.csv("summaries/nightly-stats.csv", header=F,
                         col.names=c('year',
                                     'month',
                                     'day',
                                     'satellite',
                                     'filtered_count',
                                     'raw_count',
                                     'mean',
                                     'min',
                                     'median',
                                     'max',
                                     'var',
                                     'li_median',
                                     'li_mean'))
nightlystats$year <- factor(nightlystats$year)
nightlystats$satellite <- factor(nightlystats$satellite) # not strictly necessary
reg <- lm(median ~ satellite + year, data=nightlystats)
summary(reg)

# Results:
# Call:
# lm(formula = median ~ satellite + year, data = nightlystats)
# 
# Residuals:
#    Min     1Q Median     3Q    Max 
# -6.302 -1.211 -0.320  0.769 46.297 
# 
# Coefficients: (1 not defined because of singularities)
#              Estimate Std. Error t value Pr(>|t|)    
# (Intercept)   4.90106    0.13053  37.546  < 2e-16 ***
# satelliteF12  1.24454    0.22390   5.558 2.78e-08 ***
# satelliteF14 -0.02109    0.24017  -0.088 0.930013    
# satelliteF15  0.19450    0.24766   0.785 0.432269    
# satelliteF16  0.68629    0.25692   2.671 0.007568 ** 
# satelliteF18  1.18883    0.17488   6.798 1.11e-11 ***
# year1994     -0.43352    0.18176  -2.385 0.017092 *  
# year1995     -0.41436    0.26986  -1.535 0.124703    
# year1996     -0.87146    0.28669  -3.040 0.002373 ** 
# year1997     -0.67735    0.27817  -2.435 0.014907 *  
# year1998     -0.36024    0.27601  -1.305 0.191856    
# year1999     -0.38467    0.27612  -1.393 0.163615    
# year2000      0.15619    0.27711   0.564 0.573016    
# year2001      0.89961    0.28618   3.143 0.001674 ** 
# year2002      0.38824    0.28617   1.357 0.174917    
# year2003     -0.88476    0.28576  -3.096 0.001965 ** 
# year2004     -1.21241    0.28562  -4.245 2.20e-05 ***
# year2005     -0.98255    0.29295  -3.354 0.000799 ***
# year2006     -1.57296    0.29295  -5.369 8.05e-08 ***
# year2007     -0.72703    0.29327  -2.479 0.013188 *  
# year2008     -0.73946    0.31085  -2.379 0.017384 *  
# year2009     -1.26719    0.31954  -3.966 7.36e-05 ***
# year2010      0.55277    0.16402   3.370 0.000754 ***
# year2011     -0.85848    0.16379  -5.241 1.62e-07 ***
# year2012      0.16702    0.16391   1.019 0.308232    
# year2013           NA         NA      NA       NA    
# ---
# Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
# 
# Residual standard error: 2.196 on 11587 degrees of freedom
# Multiple R-squared:  0.1203,	Adjusted R-squared:  0.1184 
# F-statistic:    66 on 24 and 11587 DF,  p-value: < 2.2e-16