YouTipR Func Apply
# R apply() Function - Array Application
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The R apply() function is used to apply a function to the rows or columns of a matrix or array.
apply() can avoid writing explicit loops, making the code more concise and efficient.
The syntax format of the apply() function is as follows:
apply(X, MARGIN, FUN, ...)
**Parameter Description:**
* **X** Input matrix or array.
* **MARGIN** Dimension: 1 means by row, 2 means by column, c(1,2) means both rows and columns.
* **FUN** The function to apply.
* **...** Additional arguments passed to FUN.
## Example
```r
# Create Score Matrix
scores <-matrix(c(88, 92, 76, 85, 90,
90, 88, 82, 78, 95,
85, 91, 78, 88, 92),
nrow=5, ncol=3)
colnames(scores)<-c("Math", "English", "programming")
rownames(scores)<-c("Zhang San", "Li Si", "Wang Wu", "Zhao Liu", "Qian Qi")
print("Score Matrix:")
print(scores)
# Calculate Each Student's Average Score by Row
row_means <-apply(scores, 1, mean)
print("Average Score per Student:")
print(round(row_means, 1))
# Calculate the Maximum Score for Each Subject by Column
col_max <-apply(scores, 2, max)
print("Maximum Score per Subject:")
print(col_max)
Executing the above code outputs the following result:
```text
"Score Matrix:" Math English programmingZhang San 88 90 85Li Si 92 88 91Wang Wu 76 82 78Zhao Liu 85 78 88Qian Qi 90 95 92 "Average Score per Student:"Zhang San Li Si Wang Wu Zhao Liu Qian Qi87.7 90.3 78.7 83.7 92.3 "Maximum Score per Subject:"Math English programming 92 95 92
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