Matlab interp1函数的C实现(线性插值)
你知道MatlabInterp1函数的任何C实现吗(仅仅是“线性”函数)?我知道一个。你可以看看GSL(数字科学图书馆)。有许多类似Matlab的函数,其中包括一维插值函数Matlab interp1函数的C实现(线性插值),c,matlab,linear-interpolation,C,Matlab,Linear Interpolation,你知道MatlabInterp1函数的任何C实现吗(仅仅是“线性”函数)?我知道一个。你可以看看GSL(数字科学图书馆)。有许多类似Matlab的函数,其中包括一维插值函数 我现在正在打电话,抱歉,无法提供链接。您知道吗?它从Matlab代码自动生成c/c++代码。如果你的Matlab软件包中有这个函数,你可以通过它运行interp1函数,看看Matlab给出了什么。在这本书中可以找到常用函数的优秀实现,这本书可以在线免费查看。第3.1.2章有一个线性插值公式,本章其余部分将介绍更高级的公式 我
我现在正在打电话,抱歉,无法提供链接。您知道吗?它从Matlab代码自动生成c/c++代码。如果你的Matlab软件包中有这个函数,你可以通过它运行interp1函数,看看Matlab给出了什么。在这本书中可以找到常用函数的优秀实现,这本书可以在线免费查看。第3.1.2章有一个线性插值公式,本章其余部分将介绍更高级的公式
我可以强烈推荐这本书,它写得非常好,涵盖了大量的算法,这些算法也是以一种非常有效且仍然可以理解的方式实现的。我自己实现了这个线性插值(抱歉,其中一些是用西班牙语编写的)。名为encuteRavalorMasProximo的函数仅查找数组(xD)中与另一个(xx[i])最近的值(elementomaproximo)和索引(indicenVector)
void interp1(int*x,int x_tam,double*y,int*xx,int xx_tam,double*yy)
{
双*dx,*dy,*slope,*intercept,*elementomaproximo,*xD;
int i,*指示向量;
dx=(双*)calloc(x_tam-1,sizeof(双));
dy=(双*)calloc(x_tam-1,sizeof(双));
斜率=(双*)calloc(x_tam-1,尺寸(双));
截距=(双*)calloc(x_tam-1,sizeof(双));
indicenVector=(int*)malloc(sizeof(int));
elementomaproximo=(双*)malloc(sizeof(双));
xD=(双*)calloc(x_tam,sizeof(双));
对于(i=0;i我已经将路易斯的代码移植到C++中。它看起来很有用,但是我没有太多检查过,所以请注意并重新检查你的结果。< /P>
#include <vector>
#include <cfloat>
#include <math.h>
vector< float > interp1( vector< float > &x, vector< float > &y, vector< float > &x_new )
{
vector< float > y_new;
y_new.reserve( x_new.size() );
std::vector< float > dx, dy, slope, intercept;
dx.reserve( x.size() );
dy.reserve( x.size() );
slope.reserve( x.size() );
intercept.reserve( x.size() );
for( int i = 0; i < x.size(); ++i ){
if( i < x.size()-1 )
{
dx.push_back( x[i+1] - x[i] );
dy.push_back( y[i+1] - y[i] );
slope.push_back( dy[i] / dx[i] );
intercept.push_back( y[i] - x[i] * slope[i] );
}
else
{
dx.push_back( dx[i-1] );
dy.push_back( dy[i-1] );
slope.push_back( slope[i-1] );
intercept.push_back( intercept[i-1] );
}
}
for ( int i = 0; i < x_new.size(); ++i )
{
int idx = findNearestNeighbourIndex( x_new[i], x );
y_new.push_back( slope[idx] * x_new[i] + intercept[idx] );
}
}
int findNearestNeighbourIndex( float value, vector< float > &x )
{
float dist = FLT_MAX;
int idx = -1;
for ( int i = 0; i < x.size(); ++i ) {
float newDist = value - x[i];
if ( newDist > 0 && newDist < dist ) {
dist = newDist;
idx = i;
}
}
return idx;
}
#包括
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向量interp1(向量&x,向量&y,向量&x\u新)
{
向量y_新;
y_new.reserve(x_new.size());
标准:向量dx,dy,斜率,截距;
dx.保留(x.大小());
dy.保留(x.大小());
坡度.储量(x.尺寸());
截距保留(x.size());
对于(int i=0;i&x)
{
浮动距离=FLT_最大值;
intidx=-1;
对于(int i=0;i0&&newDist
请参阅fileexchange中的lininterp1f。Luis提交的C代码有问题。首先,EncUserRavalorMasProximo丢失。其次,数组保留少了一个数字。我还清理了该函数。下面是带有EncUserRavalorMasProximo函数(重命名为FindNearestNeightUrIndex)的功能C代码
#包括
int FindNearestNeightUrIndex(双值,双*x,int len)
{
双区;
int-idx;
int i;
idx=-1;
dist=DBL_MAX;
对于(i=0;i0&&newDist 如果(i@user1097111,您的代码存在一个bug,在函数findnearestneaturindex中,它应该是if(newDist>=0&&newDist0&&newDist如果这对将来的某个人有帮助,这是一个没有临时数组和0 bug的版本
#include <iostream>
#include <vector>
#include <limits>
#include <cmath>
template<typename Real>
int nearestNeighbourIndex(std::vector<Real> &x, Real &value)
{
Real dist = std::numeric_limits<Real>::max();
Real newDist = dist;
size_t idx = 0;
for (size_t i = 0; i < x.size(); ++i) {
newDist = std::abs(value - x[i]);
if (newDist <= dist) {
dist = newDist;
idx = i;
}
}
return idx;
}
template<typename Real>
std::vector<Real> interp1(std::vector<Real> &x, std::vector<Real> &y, std::vector<Real> &x_new)
{
std::vector<Real> y_new;
Real dx, dy, m, b;
size_t x_max_idx = x.size() - 1;
size_t x_new_size = x_new.size();
y_new.reserve(x_new_size);
for (size_t i = 0; i < x_new_size; ++i)
{
size_t idx = nearestNeighbourIndex(x, x_new[i]);
if (x[idx] > x_new[i])
{
dx = idx > 0 ? (x[idx] - x[idx - 1]) : (x[idx + 1] - x[idx]);
dy = idx > 0 ? (y[idx] - y[idx - 1]) : (y[idx + 1] - y[idx]);
}
else
{
dx = idx < x_max_idx ? (x[idx + 1] - x[idx]) : (x[idx] - x[idx - 1]);
dy = idx < x_max_idx ? (y[idx + 1] - y[idx]) : (y[idx] - y[idx - 1]);
}
m = dy / dx;
b = y[idx] - x[idx] * m;
y_new.push_back(x_new[i] * m + b);
}
return y_new;
}
int main() {
vector<float> x{1, 2, 3, 4, 5};
vector<float> y{5, 6, 7, 8, 9};
vector<float> newx{0, 5, 6.123, 12.123, 2, 4};
auto res = interp1(x, y, newx);
for (auto i: res)
cout << i << " ";
cout << endl;
}
#包括
#包括
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模板
int近邻索引(标准::向量和x,实值和值)
{
实距离=标准::数值限制::最大值();
实际新距离=距离;
大小\u t idx=0;
对于(大小i=0;i0?(x[idx]-x[idx-1]):(x[idx+1]-x[idx]);
dy=idx>0?(y[idx]-y[idx-1]):(y[idx+1]-y[idx]);
}
其他的
{
dx=idx 我尝试过,但它是难以辨认的。1是因为。但是,它太重,不能只用于一个函数,但它可以作为替代。他特别要求C实现,所以这不是一个真正的合适的答案。这是好的,因为我正在寻找一个C++实现。谢谢!
#include <vector>
#include <cfloat>
#include <math.h>
vector< float > interp1( vector< float > &x, vector< float > &y, vector< float > &x_new )
{
vector< float > y_new;
y_new.reserve( x_new.size() );
std::vector< float > dx, dy, slope, intercept;
dx.reserve( x.size() );
dy.reserve( x.size() );
slope.reserve( x.size() );
intercept.reserve( x.size() );
for( int i = 0; i < x.size(); ++i ){
if( i < x.size()-1 )
{
dx.push_back( x[i+1] - x[i] );
dy.push_back( y[i+1] - y[i] );
slope.push_back( dy[i] / dx[i] );
intercept.push_back( y[i] - x[i] * slope[i] );
}
else
{
dx.push_back( dx[i-1] );
dy.push_back( dy[i-1] );
slope.push_back( slope[i-1] );
intercept.push_back( intercept[i-1] );
}
}
for ( int i = 0; i < x_new.size(); ++i )
{
int idx = findNearestNeighbourIndex( x_new[i], x );
y_new.push_back( slope[idx] * x_new[i] + intercept[idx] );
}
}
int findNearestNeighbourIndex( float value, vector< float > &x )
{
float dist = FLT_MAX;
int idx = -1;
for ( int i = 0; i < x.size(); ++i ) {
float newDist = value - x[i];
if ( newDist > 0 && newDist < dist ) {
dist = newDist;
idx = i;
}
}
return idx;
}
#include <float.h>
int findNearestNeighbourIndex( double value, double *x, int len )
{
double dist;
int idx;
int i;
idx = -1;
dist = DBL_MAX;
for ( i = 0; i < len; i++ ) {
double newDist = value - x[i];
if ( newDist > 0 && newDist < dist ) {
dist = newDist;
idx = i;
}
}
return idx;
}
void interp1(double *x, int x_tam, double *y, double *xx, int xx_tam, double *yy)
{
double dx, dy, *slope, *intercept;
int i, indiceEnVector;
slope=(double *)calloc(x_tam,sizeof(double));
intercept=(double *)calloc(x_tam,sizeof(double));
for(i = 0; i < x_tam; i++){
if(i<x_tam-1){
dx = x[i + 1] - x[i];
dy = y[i + 1] - y[i];
slope[i] = dy / dx;
intercept[i] = y[i] - x[i] * slope[i];
}else{
slope[i]=slope[i-1];
intercept[i]=intercept[i-1];
}
}
for (i = 0; i < xx_tam; i++) {
indiceEnVector = findNearestNeighbourIndex( xx[i], x, x_tam);
if (indiceEnVector != -1)
yy[i]=slope[indiceEnVector] * xx[i] + intercept[indiceEnVector];
else
yy[i]=DBL_MAX;
}
free(slope);
free(intercept);
}
#include <iostream>
#include <vector>
#include <limits>
#include <cmath>
template<typename Real>
int nearestNeighbourIndex(std::vector<Real> &x, Real &value)
{
Real dist = std::numeric_limits<Real>::max();
Real newDist = dist;
size_t idx = 0;
for (size_t i = 0; i < x.size(); ++i) {
newDist = std::abs(value - x[i]);
if (newDist <= dist) {
dist = newDist;
idx = i;
}
}
return idx;
}
template<typename Real>
std::vector<Real> interp1(std::vector<Real> &x, std::vector<Real> &y, std::vector<Real> &x_new)
{
std::vector<Real> y_new;
Real dx, dy, m, b;
size_t x_max_idx = x.size() - 1;
size_t x_new_size = x_new.size();
y_new.reserve(x_new_size);
for (size_t i = 0; i < x_new_size; ++i)
{
size_t idx = nearestNeighbourIndex(x, x_new[i]);
if (x[idx] > x_new[i])
{
dx = idx > 0 ? (x[idx] - x[idx - 1]) : (x[idx + 1] - x[idx]);
dy = idx > 0 ? (y[idx] - y[idx - 1]) : (y[idx + 1] - y[idx]);
}
else
{
dx = idx < x_max_idx ? (x[idx + 1] - x[idx]) : (x[idx] - x[idx - 1]);
dy = idx < x_max_idx ? (y[idx + 1] - y[idx]) : (y[idx] - y[idx - 1]);
}
m = dy / dx;
b = y[idx] - x[idx] * m;
y_new.push_back(x_new[i] * m + b);
}
return y_new;
}
int main() {
vector<float> x{1, 2, 3, 4, 5};
vector<float> y{5, 6, 7, 8, 9};
vector<float> newx{0, 5, 6.123, 12.123, 2, 4};
auto res = interp1(x, y, newx);
for (auto i: res)
cout << i << " ";
cout << endl;
}