/*!
Initialize the row vector from a part of an input row vector \e v.
\param v : Input row vector used for initialization.
\param c : column index in \e v that corresponds to the first element of the row vector to contruct.
\param ncols : Number of columns of the constructed row vector.
The sub-vector starting from v[c] element and ending on v[c+ncols-1] element
is used to initialize the contructed row vector.
The following code shows how to use this function:
\code
#include <visp3/core/vpRowVector.h>
int main()
{
vpRowVector v(4);
int val = 0;
for(size_t i=0; i<v.getCols(); i++) {
v[i] = val++;
}
std::cout << "v: " << v << std::endl;
vpRowVector w;
w.init(v, 1, 2);
std::cout << "w: " << w << std::endl;
}
\endcode
It produces the following output:
\code
v: 0 1 2 3
w: 1 2
\endcode
*/
void
vpRowVector::init(const vpRowVector &v, unsigned int c, unsigned int ncols)
{
unsigned int cncols = c+ncols ;
if (cncols > v.getCols())
throw(vpException(vpException::dimensionError,
"Bad column dimension (%d > %d) used to initialize vpRowVector",
cncols, v.getCols()));
resize(ncols);
if (this->rowPtrs == NULL) // Fix coverity scan: explicit null dereferenced
return; // Noting to do
for (unsigned int i=0 ; i < ncols; i++)
(*this)[i] = v[i+c];
}
/*!
Compute the standard deviation value of all the elements of the vector.
*/
double
vpRowVector::stdev(const vpRowVector &v, const bool useBesselCorrection)
{
if (v.data==NULL) {
throw(vpException(vpException::fatalError,
"Cannot compute mean value of an empty row vector"));
}
double mean_value = mean(v);
double sum_squared_diff = 0.0;
for(unsigned int i = 0; i < v.size(); i++) {
sum_squared_diff += (v[i]-mean_value) * (v[i]-mean_value);
}
double divisor = (double) v.size();
if(useBesselCorrection && v.size() > 1) {
divisor = divisor-1;
}
return std::sqrt(sum_squared_diff / divisor);
}