가. 데이터 분석 함수
– max(x): 최대값, min(x): 최소값, mean(x): 평균값, median(x): 중간값
– sum(x): 합, prod(x): 누적곱, cumsum(x): 누적합, cumprod(x): 누적곱
– sort(x): 정렬, var(x): 분산, std(x): 표준편차
나. 퓨리에 변환 – fft(x)
– Matlab 내의 doc fft 내용
>>Fs = 1000; % Sampling frequency
>>T = 1/Fs; % Sample time
>>L = 1000; % Length of signal
>>t = (0:L-1)*T; % Time vector
% Sum of a 50 Hz sinusoid and a 120 Hz sinusoid
>>x = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t);
>>y = x + 2*randn(size(t)); % Sinusoids plus noise
>>subplot(121)
>>plot(Fs*t(1:50),y(1:50))
>>title(‘Signal Corrupted with Zero-Mean Random Noise’)
>>xlabel(‘time (milliseconds)’)
>>NFFT = 2^nextpow2(L); % Next power of 2 from length of y
>>Y = fft(y,NFFT)/L;
>>f = Fs/2*linspace(0,1,NFFT/2);
% Plot single-sided amplitude spectrum.
>>subplot(122)
>>plot(f,2*abs(Y(1:NFFT/2)))
>>title(‘Single-Sided Amplitude Spectrum of y(t)’)
>>xlabel(‘Frequency (Hz)’)
>>ylabel(‘|Y(f)|’)
13. 데이터 분석
