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I'm trying to implement a basic sinewave signal using arrays, but I'm
having difficulty (I'm a complete beginner!)
This is what I have so far:
using namespace std;
double signal(double sinewave, double x);
int main()
{
double x, sinewave, output;
cout<<endl<<"Please enter a value, x"<<endl<<endl;
cin>>x;
output = signal(sinewave,x);
cout<<endl<<"Sin(x) = "<<output<<endl<<endl;
return 0;
}
double signal(double sinewave, double x)
{
sinewave = sin(x);
return sinewave;
}
I want to swap a single value x, for an array of 100 points.
Can anyone help me with this?
Later, I'll need to change the frequency of the signal, but this
doesn't matter now? Also, I'll want to plot the signal, but I think
this is advanced.
If anyone can help, I would really appreciated it!
Phil Newman  
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Phil Newman wrote: I'm trying to implement a basic sinewave signal using arrays, but I'm having difficulty (I'm a complete beginner!)
This is what I have so far:
using namespace std;
double signal(double sinewave, double x);
int main() {
double x, sinewave, output;
cout<<endl<<"Please enter a value, x"<<endl<<endl; cin>>x;
output = signal(sinewave,x); cout<<endl<<"Sin(x) = "<<output<<endl<<endl;
return 0; }
double signal(double sinewave, double x) {
sinewave = sin(x); return sinewave; }
I want to swap a single value x, for an array of 100 points.
Can anyone help me with this?
Later, I'll need to change the frequency of the signal, but this doesn't matter now? Also, I'll want to plot the signal, but I think this is advanced.
If anyone can help, I would really appreciated it!
Phil Newman
Try this:
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
void FillSin( vector<double>& v )
{
static const double PI = 4*atan(1.0);
for( int n=0; n < output.size(); ++n )
{
v[ n ] = sin( 2*PI / n );
}
}
int main()
{
vector<double> output( 100 );
FillSin( output );
for( int n=0; n < output.size(); ++n )
{
cout << output[n] << '\n';
}
return 0;
}
Cheers! M  
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mlimber wrote: Phil Newman wrote:
I'm trying to implement a basic sinewave signal using arrays, but I'm having difficulty (I'm a complete beginner!)
This is what I have so far:
[snip] I want to swap a single value x, for an array of 100 points.
Can anyone help me with this?
Later, I'll need to change the frequency of the signal, but this doesn't matter now? Also, I'll want to plot the signal, but I think this is advanced.
If anyone can help, I would really appreciated it!
Phil Newman
Try this:
#include <iostream> #include <vector> #include <cmath>
using namespace std;
void FillSin( vector<double>& v ) { static const double PI = 4*atan(1.0); for( int n=0; n < output.size(); ++n ) { v[ n ] = sin( 2*PI / n );
Division by Zero !!
} }
int main() { vector<double> output( 100 ); FillSin( output ); for( int n=0; n < output.size(); ++n ) { cout << output[n] << '\n'; } return 0; }
Stefan

Stefan Naewe
naewe.s_AT_atlas_DOT_de  
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Thanks. Unfortunately, the code won't compile. i get an error saying:
In function 'void FillSin(std::vector<double, std::allocator<double> &)':
'output' undeclared
Can you help there?
Thanks,
Phil  
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[...] #include <iostream> #include <vector> #include <cmath>
using namespace std;
void FillSin( vector<double>& v ) { static const double PI = 4*atan(1.0); for( int n=0; n < output.size(); ++n )
^^^
this wont compile
you mean v, not output
{ v[ n ] = sin( 2*PI / n ); }
{} are optional
matter of personal preference
}
int main() { vector<double> output( 100 ); FillSin( output ); for( int n=0; n < output.size(); ++n ) { cout << output[n] << '\n'; } return 0; }
I have not used C++ for ages but I recall that one could use
std::transform on a vector
something like
#include <functional>
or
#include <algorithm>
std::transform(v.begin(), v.end(), std::sin)
and see the result
std::copy(v.begin(), s.end(), std::ostream<int>(std::cout, " : "));
hth, Daniel
ps: well about ploting C++ has nothing builtin, nothing standard so to
say, you will have to use yours op libraries
nowdays I code in python there you could use Tk or ploting modules
matplotlib, scipy and Numeric  
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> mlimber <ml*****@gmail.com> wrote: #include <iostream> #include <vector> #include <cmath>
using namespace std;
void FillSin( vector<double>& v ) { static const double PI = 4*atan(1.0); for( int n=0; n < output.size(); ++n ) { v[ n ] = sin( 2*PI / n ); } }
int main() { vector<double> output( 100 ); FillSin( output ); for( int n=0; n < output.size(); ++n ) { cout << output[n] << '\n'; } return 0; }
Phil Newman <ph************@hotmail.com> wrote: Thanks. Unfortunately, the code won't compile. i get an error saying:
In function 'void FillSin(std::vector<double, std::allocator<double>&)':
'output' undeclared
Please quote the message you are replying to (I have pasted it in
manually).
In FillSin, either change it to:
void FillSin( vector<double>& output )
or in the for loop, change it to:
for (int n = 0; n < v.size(), ++n)

Marcus Kwok  
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yay, thanks :) that worked nicely.
cheers for the help,
I get the feeling i'll be posting a few more questions on here!
Phil  
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Stefan Näwe wrote: mlimber wrote: Phil Newman wrote:
I'm trying to implement a basic sinewave signal using arrays, but I'm having difficulty (I'm a complete beginner!)
This is what I have so far:
[snip] I want to swap a single value x, for an array of 100 points.
Can anyone help me with this?
Later, I'll need to change the frequency of the signal, but this doesn't matter now? Also, I'll want to plot the signal, but I think this is advanced.
If anyone can help, I would really appreciated it!
Phil Newman
Try this:
#include <iostream> #include <vector> #include <cmath>
using namespace std;
void FillSin( vector<double>& v ) { static const double PI = 4*atan(1.0); for( int n=0; n < output.size(); ++n ) { v[ n ] = sin( 2*PI / n );
Division by Zero !!
Oops, sorry. I just wrote that offthecuff. It should be:
for( int n=0; n < v.size(); ++n )
{
v[ n ] = sin( 2*PI / (n+1) );
}
Cheers! M  
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 Try this:
#include <iostream> #include <vector> #include <cmath>
using namespace std;
void FillSin( vector<double>& v ) { static const double PI = 4*atan(1.0); for( int n=0; n < output.size(); ++n ) { v[ n ] = sin( 2*PI / n );
The sine function has a period of 2*PI, so it should be:
v[n] = sin(2*PI*n / v.size());
for n = [ 0 ; v.size()1 ]
} }
int main() { vector<double> output( 100 ); FillSin( output ); for( int n=0; n < output.size(); ++n ) { cout << output[n] << '\n'; } return 0; }
Cheers! M
Cheers mate!
M  
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Thanks, that works great.
How would I be able to add white noise to the sinewave signal over 1000
samples?
Phil  
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"Phil Newman" wrote: How would I be able to add white noise to the sinewave signal over 1000 samples?
Since no one has responded ....
Here's what I would do but I can't certify anything.
Decide how much noise you want and use rand() to generate a voltage in that
range for a
particular sample. For each sample add the two components to get signal
plus noise. Make a second drawing from rand() to choose the polarity of the
noise. You could speed that up, at the expense of clarity, by selecting a
bit from a single drawing to define the polarity  
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> I have not used C++ for ages but I recall that one could use std::transform on a vector something like #include <functional> or #include <algorithm>
It's in <algorithm>
std::transform(v.begin(), v.end(), std::sin)
Then don't forget to fill the vector with increasing angles first. and see the result std::copy(v.begin(), s.end(), std::ostream<int>(std::cout, " : "));
Perhaps you mean:
std::copy(
v.begin(),
v.end(),
std::ostream_iterator<double>(std::cout, " : "));
hth, Daniel
ps: well about ploting C++ has nothing builtin, nothing standard so to say, you will have to use yours op libraries nowdays I code in python there you could use Tk or ploting modules matplotlib, scipy and Numeric
Not so. You can plot on the text console with letters or punctuations,
although not as good looking as most other means.
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 replies: 11
 date asked: Nov 2 '05
