Sorting with order() in R Programming - Step-by-Step Execution

Concept Flow - Sorting with order()

Input vector

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Call order()

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Compute indices for sorted order

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Use indices to reorder vector

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Return sorted vector

The order() function finds the positions that would sort a vector, then we use these positions to rearrange the vector in sorted order.

Execution Sample

R Programming

x <- c(30, 10, 20)
idx <- order(x)
sorted_x <- x[idx]
print(sorted_x)

This code sorts the vector x by getting the order indices and then reordering x accordingly.

Execution Table

Step	Action	Input/Variable	Result/Output
1	Define vector x	x = c(30, 10, 20)	x = (30, 10, 20)
2	Call order(x)	x = (30, 10, 20)	idx = (2, 3, 1)
3	Reorder x using idx	x = (30, 10, 20), idx = (2, 3, 1)	sorted_x = (10, 20, 30)
4	Print sorted_x	sorted_x = (10, 20, 30)	Output: 10 20 30

💡 All steps complete, vector sorted using order indices.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
x	(30, 10, 20)	(30, 10, 20)	(30, 10, 20)	(30, 10, 20)
idx	undefined	(2, 3, 1)	(2, 3, 1)	(2, 3, 1)
sorted_x	undefined	undefined	(10, 20, 30)	(10, 20, 30)

Key Moments - 2 Insights

Why does order(x) return indices instead of the sorted values directly?

order(x) returns the positions that would sort x, not the sorted values themselves. This lets you reorder x or related vectors consistently, as shown in step 2 of the execution_table.

How does using idx to reorder x produce the sorted vector?

Using x[idx] rearranges x by the positions in idx, which are sorted order indices. This is shown in step 3 where sorted_x becomes (10, 20, 30).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of idx after step 2?

A (1, 2, 3)

B (3, 1, 2)

C (2, 3, 1)

D (10, 20, 30)

💡 Hint

Check the 'Result/Output' column for step 2 in execution_table.

At which step is the vector actually sorted?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for when sorted_x is assigned the reordered vector in execution_table.

If x was c(5, 3, 8), what would order(x) return?

A (2, 1, 3)

B (1, 2, 3)

C (3, 2, 1)

D (2, 3, 1)

💡 Hint

order(x) returns indices that sort x ascending; check variable_tracker logic.

Concept Snapshot

order(x) returns indices that sort vector x.
Use x[order(x)] to get sorted values.
Indices show positions of sorted elements.
Useful for sorting related data consistently.
Works for numeric, character, and factor vectors.

Full Transcript

This visual trace shows how the R function order() works to sort a vector. First, we define a vector x with values 30, 10, and 20. Then, order(x) returns the indices (2, 3, 1) which represent the positions of x's elements in ascending order. Using these indices to reorder x gives the sorted vector (10, 20, 30). Finally, printing sorted_x outputs the sorted values. This method separates finding the order from applying it, which is useful for sorting multiple related vectors the same way.