price <- c(100, 110, 120, 130, 140, 150, 160, 170, 180, 190)
marketing_cost <- c(20, 25, 22, 30, 35, 40, 42, 45, 50, 55)
stores <- c(50, 52, 55, 58, 60, 62, 65, 67, 70, 72)
income <- c(5000, 5200, 5400, 5600, 5800, 6000, 6200, 6400,6600, 6800)
sales_volume <- c(200, 220, 210, 230, 240, 250, 260, 270, 280, 290)
data <- data.frame(price, marketing_cost, stores, income, sales_volume)
model <- lm(sales_volume ~ price +marketing_cost + stores + income, data =data)
summary(model)
##
## Call:
## lm(formula = sales_volume ~ price + marketing_cost + stores +
## income, data = data)
##
## Residuals:
## Min 1Q Median 3Q Max
## -3.5778 -1.5081 -0.0229 1.4289 4.4748
##
## Coefficients: (1 not defined because of singularities)
## Estimate Std. Error t value Pr(>|t|)
## (Intercept) 172.6154 83.1662 2.076 0.0832 .
## price 0.5164 0.9521 0.542 0.6071
## marketing_cost 1.9689 0.5688 3.462 0.0134 *
## stores -1.2139 3.4233 -0.355 0.7350
## income NA NA NA NA
## ---
## Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
##
## Residual standard error: 3.059 on 6 degrees of freedom
## Multiple R-squared: 0.9932, Adjusted R-squared: 0.9898
## F-statistic: 291.8 on 3 and 6 DF, p-value: 6.882e-07
pairs(data, main = "Scatterplot Matrix", pch = 19)
plot(model$residuals, main="Residual Plot", ylab="Residuals"
, xlab="Fitted Values")
abline(h = 0, col="red", lwd=2)
