假设我有两个矩阵A和B，并且我想计算A [1，]和B [2，]的内积。使用R我可以编写这段代码
class Food(models.Model):
name = models.CharField(max_length=100)
grocery_aisle = models.ManytoManyField(Store, through='Location')
class Store(models.Model):
name = models.CharField(max_length=100)
aisles = { # Not really sure how to store this kind of information which would be different for each Store object.
0: 'Produce Section',
1: 'Aisle 1: bread and peanutbutter',
2: 'Frozen Desserts',
3: 'Pharmacy'
}
class Location(models.Model):
food = models.ForeignKey(Food, on_delete=models.CASCADE)
store = models.ForeignKey(Store, on_delete=models.CASCADE)
aisle = models.SmallIntegerField(choices=MEASUREMENT_CHOICES) # option descriptions depend on selected store object
我正在尝试学习如何使用set.seed(1982)
A <- matrix(rnorm(12,2,1), ncol = 4)
B <- matrix(rnorm(20,2,1), ncol = 4)
a <- A[1,]
b <- B[2,]
a %*% b
19.63588
做同样的事情。我写了以下代码：
Rcpp编译器告诉我它无法进行此转换：
#include <Rcpp.h>
#include <numeric>
using namespace Rcpp;
// [[Rcpp::export]]
double myInnerProduct(const NumericMatrix A,
const NumericMatrix B,
const int n,
const int i){
std::vector<double> a = A(n,_) ;
std::vector<double> b = B(i,_) ;
double val = std::inner_product(a.begin(), a.end(), b.begin(), 0);
return val;
}
/*** R
set.seed(1982)
A <- matrix(rnorm(12,2,1), ncol = 4)
B <- matrix(rnorm(20,2,1), ncol = 4)
a <- A[1,]
b <- B[2,]
a %*% b
myInnerProduct(A, B, 1, 2)
*/
我该如何解决？