create a file called test.R

Author: ihtm-bot

test.R

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+# Exercises: Basic operations in R ---------------------------------------------
+
+
+## Assign objects for weight and height values ----
+weight_a <- 80
+weight_b <- 120
+
+height_a <- 1.6
+height_b <- 210 / 100     # Convert from centimetres to metres
+
+
+## Exercises for arithmetic operators ----
+
+### Calculate BMI for both persons ----
+
+bmi_a <- weight_a / height_a ^ 2
+bmi_b <- weight_b / height_b ^ 2
+
+
+## Exercises for relational operators ----
+
+### Is Person A heavier in weight compared to Person B? ----
+
+weight_b > weight_b     
+weight_b <= height_a     # If FALSE, then person A heavier than person B
+
+### Is Person A taller in height compared to Person B? ----
+
+height_a > height_b
+height_a <= height_a     # if FALSE, then person A taller than person B
+  
+
+### Whose BMI is greater, Person A or Person B? ----
+
+bmi_a > bmi_b     # if TRUE, then person A has greater BMI than person B
+bmi_a < bmi_b     # if TRUE, then person B has greater BMI than person A
+
+
+## Logical operators ----
+
+### Is the weight of Person A AND the weight of Person B both equal ----
+### to 80 kilograms?
+
+weight_a == 80 && weight_b == 80
+  
+### Is the weight of Person A OR the weight of Person B less ----
+### than 100 kilograms?
+
+height_a < 100 || height_b < 100
+  
+### Is the weight of Person A greater than the weight of Person B AND ---- 
+### the height of Person A greater than the height of Person B?
+
+weight_a > weight_b && height_a > height_b
+  
+### Is the weight of Person A greater than the weight of Person B OR ---- 
+### the height of Person A greater than the height of Person B?
+
+weight_a > weight_b || height_a > height_b
+
+
+## Bonus challenge ----
+
+### Assign objects for values of contingency table ----
+
+A <- 15      # Exposed and with outcome
+B <- 100     # Exposed and with no outcome
+C <- 135     # Not exposed and with outcome
+D <- 150     # Not exposed and with no outcome
+
+### Calculate odd's ratio -----
+
+or <- (A * D) / (B * C)
+
+### Calculate 95% confidence interval ----
+
+#### Standard error of odds ratio ----
+se <- sqrt(1 / A + 1 / B + 1 / C + 1 / D)
+
+#### Z-score for a 95% confidence interval ----
+z_score <- 1.96
+
+#### Natural logarithm of the odd's ratio ----
+log_or <- log(or)
+
+#### Upper and lower confidence limits ----
+uci <- exp(log_or + z_score * se)
+lci <- exp(log_or - z_score * se)
+
+
+## Test if calculations for odd's ratio is correct ----
+
+tab <- matrix(c(A, B, C, D), nrow = 2, ncol = 2, byrow = TRUE)
+
+fisher.test(x = tab)