[英]Specifically assign contrasts in R model.matrix
If I have a variable (condition) of 2 levels and want to create a model.matrix R automatically assigns conditionB as the term in the design matrix. 如果我有2个级别的变量(条件)并要创建模型,矩阵R会自动将conditionB分配为设计矩阵中的项。
condition <- as.factor( c("A","A","A","B","B","B"))
df <- data.frame(condition)
design <- model.matrix( ~ condition)
> df
condition
1 A
2 A
3 A
4 B
5 B
6 B
> design
(Intercept) conditionB
1 1 0
2 1 0
3 1 0
4 1 1
5 1 1
6 1 1
attr(,"assign")
[1] 0 1
attr(,"contrasts")
attr(,"contrasts")$condition
[1] "contr.treatment"
Question : I would like to have my results relative to conditionA . 问题 :我希望得到与conditionA相关的结果。 How can I specify this in model.matrix() ? 如何在model.matrix()中指定呢?
(A workaround would be to inverse the resulting FCs) (一种解决方法是将生成的FC求逆)
You can use the C
function to determine the base that you want to be taken into consideration: 您可以使用C
函数来确定要考虑的基数:
Taking A as the base: 以A为基数:
model.matrix(~C(condition,base=1))
(Intercept) C(condition, base = 1)2
1 1 0
2 1 0
3 1 0
4 1 1
5 1 1
6 1 1
attr(,"assign")
[1] 0 1
attr(,"contrasts")
attr(,"contrasts")$`C(condition, base = 1)`
2
A 0
B 1
Taking B as the base: 以B为基数:
model.matrix(~C(condition,base=2))
(Intercept) C(condition, base = 2)1
1 1 1
2 1 1
3 1 1
4 1 0
5 1 0
6 1 0
attr(,"assign")
[1] 0 1
attr(,"contrasts")
attr(,"contrasts")$`C(condition, base = 2)`
1
A 1
B 0
Is it the result you want? 是您想要的结果吗?
df <- data.frame(condition)
design <- model.matrix( ~ condition-1)
design
conditionA conditionB
1 1 0
2 1 0
3 1 0
4 0 1
5 0 1
6 0 1
attr(,"assign")
[1] 1 1
attr(,"contrasts")
attr(,"contrasts")$`condition`
[1] "contr.treatment"
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