Pushback

[Chandrashekar]

hi,

I am facing problem with pushback() method in Vectors. I am getting
compilation errors when I am using pushabck() in the following
program. I am pasting the code here

/*************** *************** **********/

#include<iostre am>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

class Moving_Average{
public:
std::vector<dou ble> forecast;
// vector<double>f orecast;

public:
Moving_Average( int size) {
cout<<" IN size "<<endl;
forecast.resize (size);
cout<<" Out sized "<<endl;
}

void calculate(doubl e *da,int time) {

/* This function is merely copying the elements of vector "data" into
vector "forecast"
*/
for(int i=0;i<time;i++) {
forecast.pushba ck(*(da+i)); // I am facing problem here
// ^^^^^^^^
}
}
void prasint(int time) {
for(int i=0;i<time;i++) {
cout<<"asd "<<forecast[i]<<endl;
}
}
};


int main()
{
int periods;
cout<<"Enter the no.of periods of historic data"<<endl;
cin>>periods;
vector<double>d ata(periods);
for(int i=0;i<periods;i ++) {
cout<<"Enter data for period --> "<<i<<" ";
cin>>data[i];
}
Moving_Average MA(periods);
MA.calculate(da ta.begin(),peri ods);
MA.prasint(peri ods);
}

/*************** *************** *************** **************/
When I used pish_back() in place of pushback(), i didnt get any
compilation errors.But, I am not getting proper output. In the above
program I am copying
the elements of vector 'data' (i.e da) to vector forecast.Here is the
sample out put
/*************** ***************/

Enter the no.of periods of historic data
3
Enter data for period --> 0 1
Enter data for period --> 1 2
Enter data for period --> 2 3

IN calc value is -->1
Out of cal value is -->2
Out of cal value is -->3
Out of cal
in print
asd 1.88323e-307
asd 1.88323e-307
asd 1.88323e-307

/*************** *************** *************** ***/

Can somebody tell me what is the difference between pushback() and
push_back()? Is there any better method to store values in vectors
other than this?

Thanks,

Chandrashekar

[Victor Bazarov]

Re: Pushback

"Chandrashe kar" <chandrak@bhelh yd.co.in> wrote...[color=blue]
> I am facing problem with pushback() method in Vectors. I am getting
> compilation errors when I am using pushabck() in the following
> program. I am pasting the code here[/color]

There is not member function 'pushback' in 'vector'. There
is, however, the member function 'push_back'. RTFM.

And if you're not getting "correct output", you have to post
your code and explain what output you expect as "correct"
and why.

Victor

[Chandrashekar]

Re: Pushback

"Victor Bazarov" <v.Abazarov@att Abi.com> wrote in message news:<6MoQa.552 29$N7.7349@sccr nsc03>...[color=blue]
> "Chandrashe kar" <chandrak@bhelh yd.co.in> wrote...[color=green]
> > I am facing problem with pushback() method in Vectors. I am getting
> > compilation errors when I am using pushabck() in the following
> > program. I am pasting the code here[/color]
>
> There is not member function 'pushback' in 'vector'. There
> is, however, the member function 'push_back'. RTFM.
>
> And if you're not getting "correct output", you have to post
> your code and explain what output you expect as "correct"
> and why.
>
> Victor[/color]


Thanks for your reply.
My code is here
/*************** *************** **********/

#include<iostre am>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

class Moving_Average{
public:
std::vector<dou ble> forecast;
// vector<double>f orecast;

public:
Moving_Average( int size) {
cout<<" IN size "<<endl;
forecast.resize (size);
cout<<" Out sized "<<endl;
}

void calculate(doubl e *da,int time) {

/* This function is merely copying the elements of vector "data" into
vector "forecast"
*/
for(int i=0;i<time;i++) {
forecast.push_b ack(*(da+i)); // I am copying the elements of da
to forecast
}
}
void prasint(int time) {
for(int i=0;i<time;i++) {
cout<<"asd "<<forecast[i]<<endl;
}
}
};


int main()
{
int periods;
cout<<"Enter the no.of periods of historic data"<<endl;
cin>>periods;
vector<double>d ata(periods);
for(int i=0;i<periods;i ++) {
cout<<"Enter data for period --> "<<i<<" ";
cin>>data[i];
}
Moving_Average MA(periods);
MA.calculate(da ta.begin(),peri ods);
MA.prasint(peri ods);
}

/*************** *************** *************** **************/

I am getting following output
/*************** ***************/

Enter the no.of periods of historic data
3
Enter data for period --> 0 1
Enter data for period --> 1 2
Enter data for period --> 2 3

IN calc value is -->1
Out of cal value is -->2
Out of cal value is -->3
Out of cal
in print
asd 1.88323e-307
asd 1.88323e-307
asd 1.88323e-307

/*************** *************** *************** ***/
And I expect following output since I am copying the elements of one
vector to the other. (I know that there are some other ways to do it,
but I want it this way)

IN calc value is -->1
Out of cal value is -->2
Out of cal value is -->3
Out of cal
in print
asd 1
asd 2
asd 3
/*************** **********/

Chandrashekar

[Ron Natalie]

Re: Pushback


"Chandrashe kar" <chandrak@bhelh yd.co.in> wrote in message news:94ac6a9.03 07140017.39bef4 b3@posting.goog le.com...
[color=blue]
> forecast.resize (size);[/color]

push_back resizes the array to hold the additional object. You don't need to do it both.
I think you'll find your vector forecast ends up being 6 long.
[color=blue]
> forecast.push_b ack(*(da+i)); // I am copying the elements of da
> to forecast[/color]

You can either do forcast[i] = da[i] here or avoid resizing the array.

[Victor Bazarov]

Re: Pushback

"Chandrashe kar" <chandrak@bhelh yd.co.in> wrote...[color=blue]
> "Victor Bazarov" <v.Abazarov@att Abi.com> wrote in message[/color]
news:<6MoQa.552 29$N7.7349@sccr nsc03>...[color=blue][color=green]
> > "Chandrashe kar" <chandrak@bhelh yd.co.in> wrote...[color=darkred]
> > > I am facing problem with pushback() method in Vectors. I am getting[/color][/color]
> [...]
> class Moving_Average{
> public:
> std::vector<dou ble> forecast;
> // vector<double>f orecast;
>
> public:
> Moving_Average( int size) {
> cout<<" IN size "<<endl;
> forecast.resize (size);[/color]

I think John already told you to use 'reserve' here.
[color=blue]
> cout<<" Out sized "<<endl;
> }
> [...][/color]

Victor