## 
## Call:
## lm(formula = Weekly_Sales ~ . - Date, data = trainlm)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -525633  -68991  -12509   39748 1846111 
## 
## Coefficients:
##                 Estimate Std. Error t value Pr(>|t|)    
## (Intercept)    1151243.2   272157.8   4.230 2.38e-05 ***
## Store2          345185.7    23131.9  14.923  < 2e-16 ***
## Store3        -1182103.4    23860.8 -49.542  < 2e-16 ***
## Store4          780139.7   113852.5   6.852 8.26e-12 ***
## Store5        -1275756.5    24041.0 -53.066  < 2e-16 ***
## Store6          -31479.8    23051.0  -1.366 0.172116    
## Store7         -916670.9    34857.1 -26.298  < 2e-16 ***
## Store8         -717191.8    24207.0 -29.627  < 2e-16 ***
## Store9        -1062818.7    24423.8 -43.516  < 2e-16 ***
## Store10         673025.1   110260.5   6.104 1.12e-09 ***
## Store11        -220807.2    23391.9  -9.439  < 2e-16 ***
## Store12        -117652.0   103278.6  -1.139 0.254693    
## Store13         701813.5   111822.7   6.276 3.80e-10 ***
## Store14         611529.2    42897.5  14.256  < 2e-16 ***
## Store15        -653568.8   103520.8  -6.313 2.99e-10 ***
## Store16       -1008393.6    38108.0 -26.461  < 2e-16 ***
## Store17        -421318.3   112843.5  -3.734 0.000191 ***
## Store18        -166822.5   101202.5  -1.648 0.099340 .  
## Store19         179028.9   103426.0   1.731 0.083523 .  
## Store20         548748.8    25303.3  21.687  < 2e-16 ***
## Store21        -812656.4    23488.5 -34.598  < 2e-16 ***
## Store22        -263125.9    97717.3  -2.693 0.007113 ** 
## Store23          42260.6   110440.2   0.383 0.701993    
## Store24         106935.2   102340.9   1.045 0.296129    
## Store25        -848898.6    24922.1 -34.062  < 2e-16 ***
## Store26        -281187.6   103072.5  -2.728 0.006396 ** 
## Store27         490291.0    98773.4   4.964 7.17e-07 ***
## Store28         199456.1   103261.5   1.932 0.053476 .  
## Store29        -692860.5    99293.6  -6.978 3.44e-12 ***
## Store30       -1125380.1    22514.9 -49.984  < 2e-16 ***
## Store31        -174307.3    23075.9  -7.554 5.10e-14 ***
## Store32        -317341.0    34839.1  -9.109  < 2e-16 ***
## Store33        -956315.0   109823.6  -8.708  < 2e-16 ***
## Store34        -253007.9   105592.6  -2.396 0.016612 *  
## Store35        -346454.1    96218.2  -3.601 0.000321 ***
## Store36       -1190644.6    23216.4 -51.285  < 2e-16 ***
## Store37       -1032651.1    22870.9 -45.151  < 2e-16 ***
## Store38        -742825.5   103466.0  -7.179 8.16e-13 ***
## Store39        -103994.2    22905.8  -4.540 5.77e-06 ***
## Store40        -381538.0   110391.8  -3.456 0.000553 ***
## Store41        -242781.0    37135.2  -6.538 6.94e-11 ***
## Store42        -670390.8   110417.9  -6.071 1.37e-09 ***
## Store43        -857609.3    25877.4 -33.141  < 2e-16 ***
## Store44        -987424.4   112316.8  -8.791  < 2e-16 ***
## Store45        -654165.3    42482.5 -15.398  < 2e-16 ***
## Holiday_Flag1    62271.6     9505.0   6.551 6.34e-11 ***
## Temperature       -771.8      157.8  -4.892 1.03e-06 ***
## Fuel_Price      -41411.1     8552.7  -4.842 1.33e-06 ***
## CPI               3500.3     1232.7   2.839 0.004539 ** 
## Unemployment    -20854.4     5128.0  -4.067 4.85e-05 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 160600 on 4478 degrees of freedom
## Multiple R-squared:  0.9197, Adjusted R-squared:  0.9188 
## F-statistic:  1047 on 49 and 4478 DF,  p-value: < 2.2e-16
##      Store          Date            Weekly_Sales     Holiday_Flag
##  15     :  52   Length:1907        Min.   : 215359   0:1777      
##  18     :  52   Class :character   1st Qu.: 555466   1: 130      
##  3      :  51   Mode  :character   Median : 972374               
##  26     :  51                      Mean   :1051602               
##  40     :  51                      3rd Qu.:1414336               
##  21     :  50                      Max.   :3676389               
##  (Other):1600                                                    
##   Temperature       Fuel_Price         CPI         Unemployment   
##  Min.   :  5.54   Min.   :2.514   Min.   :126.1   Min.   : 3.879  
##  1st Qu.: 47.43   1st Qu.:2.909   1st Qu.:131.8   1st Qu.: 6.925  
##  Median : 62.27   Median :3.417   Median :182.0   Median : 7.907  
##  Mean   : 60.36   Mean   :3.345   Mean   :171.1   Mean   : 7.997  
##  3rd Qu.: 74.58   3rd Qu.:3.722   3rd Qu.:212.6   3rd Qu.: 8.622  
##  Max.   :100.07   Max.   :4.468   Max.   :227.2   Max.   :14.313  
##                                                                   
##  sales_predicted        res2                tot2          
##  Min.   : 231680   Min.   :8.400e+01   Min.   :1.920e+04  
##  1st Qu.: 562480   1st Qu.:6.043e+08   1st Qu.:4.058e+10  
##  Median : 977351   Median :2.747e+09   Median :2.024e+11  
##  Mean   :1052345   Mean   :2.559e+10   Mean   :3.204e+11  
##  3rd Qu.:1424534   3rd Qu.:1.138e+10   3rd Qu.:4.430e+11  
##  Max.   :2189644   Max.   :2.424e+12   Max.   :6.890e+12  
## 

1. Weekly sales increase when CPI increase

2. Weekly sales decrease when unemployment is high

3. When it is cold outside, sales decrease

r2 is 0.9, which means the model is statistically significant