public static float[] filterFFT(float[] res, double filter)
{
int reslen = res.Length;
List <float> Y = new List <float>(res);
Console.WriteLine("ydata:" + res.Length);
Console.WriteLine("a:" + Y.ToArray().Length);
Y = TWFFT.DataFill(Y);
Console.WriteLine("b:" + Y.ToArray().Length);
float[] y = new float[Y.ToArray().Length];
y = TWFFT.FFT_filter(Y.ToArray(), filter); //第二个参数可调，调整范围是：(0,1)。为1 的时候没有滤波效果，为0的时候将所有频率都过滤掉。
int putlen = TWFFT.putlen; //获取填充数据的长度的一半
Console.WriteLine("putlen:" + putlen);
Console.WriteLine("a:" + Y.ToArray().Length);
for (int i = 0; i < reslen; i++)
{
res[i] = (float)Math.Round(y[i + putlen], 2);
}
return(res);
}
public static float[] FFT_filter(double[] res, double filter)
{
//a是实部、b是虚部
float[] a = new float[res.Length];
float[] b = new float[res.Length];
List <float> ans = new List <float>();
for (int j = 0; j < res.Length; j++)
{
// Console.WriteLine("I:" + j);
a[j] = (float)res[j];
b[j] = 0.0f;
}
length = TWFFT.FFT(a, b);
//length是傅里叶变换处理过后的数组大小
//在频域上对数据进行过滤
int p = (int)(length * filter);
for (int i = 0; i < length; i++)
{
if (p < i && i < length - p)
{
a[i] = 0f;
b[i] = 0f;
}
}
length = TWFFT.IFFT(a, b);
for (int i = 0; i < length; i++)
{
//Console.WriteLine("{0}\t{1}\t{2}", i, a[i], b[i]);
ans.Add((float)Math.Sqrt(a[i] * a[i] + b[i] * b[i]));
}
return(ans.ToArray());
}