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%外部文件导入matlab进行傅里叶变换
%外部文件名字无所谓,导入之后的名字叫“data”
step1=data' % 如果导入的是两列矩阵,需要转置处理
x1=step1(1,:); % 获取转置后的第一行,自变量行
y1=step1(2,:); % 获取转置后的第二行,因变量行
figure
plot(x1,y1)
%对信号进行fft变换,获取信号频率分布
L1=length(x1); % 采样长度 应该是偶数
T1=(x1(end)-x1(1))/length(x1); % 采样周期等于采样长度除去采样点数
Fs1=1/T1; % 采样频率
f1=Fs1*(0:(L1/2))/L1;
% 傅里叶变换
S1=y1(1:L1);
Y1 = fft(S1);
P21 = abs(Y1/L1);
P11 = P21(1:L1/2+1);
P11(2:end-1) = 2*P11(2:end-1);
figure
plot(f1,P11)
xlabel('f1 (Hz)')
ylabel('|P11(f)|')
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%亲验正确
%matlab主页有“导入”,先导入外部文件Excel,再运行上面的程序
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