math.cs

简易的震动波形绘制工具

using System;

namespace nanwin
{
	/// <summary>
	/// math 的摘要说明。
	/// </summary>
	public class math
	{
		public math()
		{
			//
			// TODO: 在此处添加构造函数逻辑
			//
		}
		public static void FFT(double[] pr,double[] pi/*输入时域幅值*/,int n/*数组数据个数*/,int k,double[] fr,double[] fi,/*阿中间变量*/double[] al,double[] ph/*结果*/)
		{
			/*after FFT, real and image parts: fr fi    */
			double PI=3.1415926F;
			int i,it,m,ss,j,nv,l0;
			double p,q,s,vr,vi,poddr,poddi;
			for (it=0;it<=n-1;it++)
			{
				m=it;
				ss=0;
				for(i=0;i<=k-1;i++)
				{
					j=m/2;
					ss=2*ss+(m-2*j);
					m=j;
				}
				fr[it]=pr[ss];
				fi[it]=pi[ss];
			}
			pr[0]=1.0;pi[0]=0.0;
			p=2*PI/(1.0*n);
			pr[1]=Math.Cos(p);
			pi[1]=-Math.Sin(p);
			for(i=2;i<=n-1;i++)
			{
				p=pr[i-1]*pr[1];
				q=pi[i-1]*pi[1];
				s=(pr[i-1]+pi[i-1])*(pr[1]+pi[1]);
				pr[i]=p-q;
				pi[i]=s-p-q;
			}
			for (it=0;it<=n-2;it=it+2)
			{
				vr=fr[it];
				vi=fi[it];
				fr[it]=vr+fr[it+1];
				fi[it]=vi+fi[it+1];
				fr[it+1]=vr-fr[it+1];
				fi[it+1]=vi-fi[it+1];
			}
			m=n/2;
			nv=2;
			for (l0=k-2;l0>=0;l0--)
			{
				m=m/2;
				nv=2*nv;
				for (it=0;it<=(m-1)*nv;it=it+nv)
					for(j=0;j<=(nv/2)-1;j++)
					{
						p=pr[m*j]*fr[it+j+nv/2];
						q=pi[m*j]*fi[it+j+nv/2];
						s=pr[m*j]+pi[m*j];
						s=s*(fr[it+j+nv/2]+fi[it+j+nv/2]);
						poddr=p-q;
						poddi=s-p-q;
						fr[it+j+nv/2]=fr[it+j]-poddr;
						fi[it+j+nv/2]=fi[it+j]-poddi;
						fr[it+j]=fr[it+j]+poddr;
						fi[it+j]=fi[it+j]+poddi;
					}
			}
			for(i=0;i<=n-1;i++)
			{
				al[i]=Math.Sqrt(fr[i]*fr[i]+fi[i]*fi[i]);
				ph[i]=Math.Atan2(fi[i],fr[i]);
			}
		}
	}
						
}