I'm trying to set the value of a float by using (max_element-min_element) from a vector. I'm looping over several of these, hence the vector of floats and vector of vectors.
I'm getting the following error:
Expression: Vector iterator not dereferencable
vector<float> amplitudeStorage;
vector<vector<float>> vectorStorage;
int main(){
for (int i = 0; i < amplitudeStorage.size(); i++)
{
AssignWaveAmplitude(amplitudeStorage[i], vectorStorage[i]);
}
}
It happens on the function call. The function looks like this:
void AssignWaveAmplitude(float amplitudeVariable, vector<float> dataVectorr)
{
amplitudeVariable = (*max_element(begin(dataVectorr), end(dataVectorr))) - (*min_element(begin(dataVectorr), end(dataVectorr)));
}
Does anyone know how to fix this?
Thanks very much.
EDIT1:The solution to this problem is the first comment to this question. Some of the vectors I was using were empty, which caused the error.
EDIT2:
@WhozCraig so now I've done this:
for (int i = 0; i < amplitudeStorage.size(); i++) {
amplitudeStorage[i] =AssignWaveAmplitude(vectorStorage[i]);
}
and this:
float AssignWaveAmplitude( vector<float> dataVectorr) {
return (*max_element(begin(dataVectorr), end(dataVectorr))) - (*min_element(begin(dataVectorr), end(dataVectorr)));
}
but the floats all still come out to the same number. any idea why?
EDIT3: It turns out the reason as to why the floats were coming out wrong was because I was outputting them wrong.
I was doing: cout << lowerBackYAmplitude<< endl
(this was one of the values in amplitudeStorage)
I should have been doing:
for (int i = 0; i < amplitudeStorage.size(); i++)
{
cout << amplitudeStorage[i] << endl;
}
Your compiler is probably trying to warn you that you cannot correctly refer to amplitudeStorage[i] for any value of i, when the amplitudeStorage vector is simply empty. Either resize amplitudeStorage to match the size of vectorStorage at at the start, or use push_back
. I prefer push_back
. Here's a complete example (which also avoids passing vectors by value and corrects the problem in your code of using int
to index a data structure whose size itself can grow to more than the maximum value an int
can hold).
Note that this code is in C++11, since it uses a range-based for loop. You may need to tell your compiler to turn on support for C++11. There are lots of nice conveniences in C++11.
#include <vector>
#include <algorithm>
using namespace std;
float WaveAmplitude(const vector<float>& dataVectorr) {
return (*max_element(begin(dataVectorr), end(dataVectorr)))
- (*min_element(begin(dataVectorr), end(dataVectorr)));
}
vector<float> amplitudeStorage;
vector<vector<float>> vectorStorage;
int main(void) {
// Populate vectorStorage somehow here, replacing this comment.
amplitudeStorage.clear();
for (const auto& wave : vectorStorage)
{
amplitudeStorage.push_back(WaveAmplitude(wave));
}
return 0;
}
我使用的一些向量是空的,这导致了错误。
See full worked example. I try co compile and there is no problems.
#include <vector>
#include <algorithm>
using namespace std;
vector<float> amplitudeStorage;
vector< vector<float> > vectorStorage;
void AssignWaveAmplitude(float& amplitudeVariable, const vector<float>& dataVectorr) {
if( dataVectorr.size() ) {
amplitudeVariable = 0;
return;
}
amplitudeVariable = (*max_element(dataVectorr.begin(), dataVectorr.end())) -
(*min_element(dataVectorr.begin(), dataVectorr.end()));
}
main(){
for (int i = 0; i < amplitudeStorage.size(); i++) {
AssignWaveAmplitude(amplitudeStorage[i], vectorStorage[i]);
}
}
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