matlab常用函数之数据读取&优化程序运行时间（2）

客官°小女子只卖身不卖艺 2023-07-24 11:54 2阅读 0赞

### **如何读取数据程序进行优化？** ###

### **1、预先为变量分配内存；** ###

**（1）原始程序如下：**

程序通过fgetl()逐行读取数据，并对数据进行处理，代码如下：

profile on
    filename = 'nav_data20180129000742-3.5Hr.txt';
    %单位换算
    d2r=pi/180;
    temp=d2r/3600;
    t=[];
    freq=100;
    j=0; 
    fid=fopen(filename);
    while 1
        j=j+1;
        tline = fgetl(fid);
        if tline==-1, break, end
        nav_data=str2num(tline);
            %累计时间
        t=[t;j*1/freq];
        %xyz三轴陀螺仪rad/s
        wb(j,1) = nav_data(1,6)*temp;
        wb(j,2) = nav_data(1,7)*temp;
        wb(j,3) = nav_data(1,8)*temp;
        %xyz三轴陀螺仪温度 
        gyro_tem(j,1)= nav_data(1,9);
        gyro_tem(j,2)= nav_data(1,10);
        gyro_tem(j,3)= nav_data(1,11);
        %xyz三轴加速度计 m/s^2
        fb(j,1) =  nav_data(1,12);
        fb(j,2) =  nav_data(1,13);
        fb(j,3) =  nav_data(1,14);
        %xyz三轴加速度计温度
        acc_tem(j,1)=  nav_data(1,15);
        acc_tem(j,2)=  nav_data(1,16);
        acc_tem(j,3)=  nav_data(1,17);
    
    end
    fclose(fid);
    %保存数据
    FOG.t=t;
    FOG.wb=wb;
    FOG.fb=fb;
    FOG.freq=freq;
    FOG.gyro_tem=gyro_tem;
    FOG.acc_tem=acc_tem;
    save( 'FOG.mat','FOG')
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实际运行时间为：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1d3VrdTEyMw_size_16_color_FFFFFF_t_70][]

**（2）修改后程序如下：**

clc;    %清空命令行窗口
    clear;  %清空工作区
    close all;  
    %% read data
    profile on
    filename = 'nav_data20180129000742-3.5Hr.txt';
    %单位换算
    d2r=pi/180;
    temp=d2r/3600;
    freq=100;
    ts=1/freq;
    j=0; 
    fid=fopen(filename);
    %对变量预先分配内容
    len=5*100*3600; %采样率100HZ，按照5小时预先分配
    t=zeros(len,1);
    wb=zeros(len,3);
    gyro_tem=zeros(len,3);
    fb=zeros(len,3);
    acc_tem=zeros(len,3);
    while 1
        j=j+1;
        tline = fgetl(fid);
        if tline==-1, break, end
        nav_data=str2num(tline);
            %累计时间
    %     t=[t;j*1/freq];
        t(j,1)=j*ts;
        %xyz三轴陀螺仪rad/s
        wb(j,1) = nav_data(1,6)*temp;
        wb(j,2) = nav_data(1,7)*temp;
        wb(j,3) = nav_data(1,8)*temp;
        %xyz三轴陀螺仪温度 
        gyro_tem(j,1)= nav_data(1,9);
        gyro_tem(j,2)= nav_data(1,10);
        gyro_tem(j,3)= nav_data(1,11);
        %xyz三轴加速度计 m/s^2
        fb(j,1) =  nav_data(1,12);
        fb(j,2) =  nav_data(1,13);
        fb(j,3) =  nav_data(1,14);
        %xyz三轴加速度计温度
        acc_tem(j,1)=  nav_data(1,15);
        acc_tem(j,2)=  nav_data(1,16);
        acc_tem(j,3)=  nav_data(1,17);
    
    end
    fclose(fid);
    %% 根据数据实际长度，进行裁剪
    t(j:end,:)=[];
    wb(j:end,:)=[];
    gyro_tem(j:end,:)=[];
    fb(j:end,:)=[];
    acc_tem(j:end,:)=[];
    %保存数据
    FOG.t=t;
    FOG.wb=wb;
    FOG.fb=fb;
    FOG.freq=freq;
    FOG.gyro_tem=gyro_tem;
    FOG.acc_tem=acc_tem;
    save( 'FOG.mat','FOG')
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程序运行时间：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1d3VrdTEyMw_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1d3VrdTEyMw_size_16_color_FFFFFF_t_70 2][]

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