matlab使用

最新推荐文章于 2021-08-05 22:18:48 发布

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最新推荐文章于 2021-08-05 22:18:48 发布

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文章标签： matlab python 操作系统

1.直接在终端输入matlab打不开

　进入/usr/local/MATLAB/R2015a/bin目录，然后sudo matlab就可以打开matlab

2.GNU Octave是一个类matlab软件，可以跑matlab的代码，本身软件比matlab小很多

3.matlab下标是从一开始的

4.矩阵分解：　　

>> a=magic(5)
a =
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
>> b=[a(1:3,1:3)]
b =
    17    24     1
    23     5     7
     4     6    13
>> c=[a(1:3,4:5)]
c =
     8    15
    14    16
    20    22

和python不同，matlab中的最后一个下标是包含的。a(1:3),在matlab中是第一行到第三行，但是在python中就是第一行到第二行，不会包括第三行。a(1:3，1:3)，第一个是代表分解行，第二个是代表分解列。

matlab的下标是从1开始的，不像python从0开始

5.这是kitti将3d点云数据映射到图像上的代码（当然我修改了一些我自己的东西）：

function run_demoVelodyne (base_dir,calib_dir)
% KITTI RAW DATA DEVELOPMENT KIT
% 
% Demonstrates projection of the velodyne points into the image plane
%
% Input arguments:
% base_dir .... absolute path to sequence base directory (ends with _sync)
% calib_dir ... absolute path to directory that contains calibration files

% clear and close everything
close all; dbstop error; clc;
disp('======= KITTI DevKit Demo =======');

% options (modify this to select your sequence)
if nargin<1
  base_dir  = '/home/sensetime/kitti_raw_data/2011_09_26_sync/2011_09_26_drive_0001_sync';
end
if nargin<2
  calib_dir = '/home/sensetime/kitti_raw_data/2011_09_26_calib';
end
cam       = 2; % 0-based index
frame     = 0; % 0-based index

% load calibration
calib = loadCalibrationCamToCam(fullfile(calib_dir,'calib_cam_to_cam.txt'));
Tr_velo_to_cam = loadCalibrationRigid(fullfile(calib_dir,'calib_velo_to_cam.txt'));

% compute projection matrix velodyne->image plane
R_cam_to_rect = eye(4);
R_cam_to_rect(1:3,1:3) = calib.R_rect{1};
P_velo_to_img = calib.P_rect{cam+1}*R_cam_to_rect*Tr_velo_to_cam;

% load and display image
img = imread(sprintf('%s/image_%02d/data/%010d.png',base_dir,cam,frame));
fig = figure('Position',[20 100 size(img,2) size(img,1)]); axes('Position',[0 0 1 1]);
imshow(img); hold on;

% load velodyne points
fid = fopen(sprintf('%s/velodyne_points/data/%010d.bin',base_dir,frame),'rb');
velo = fread(fid,[4 inf],'single')';
velo    %显示出这个矩阵的所有内容
fid1=fopen('/home/sensetime/kitti_raw_data/0.txt','wt')
fprintf(fid1,'%8.4f %8.4f %8.4f %8.4f\n',velo')
fclose(fid1)    %把矩阵中所有的信息打印到txt文件上
velo = velo(1:5:end,:); % remove every 5th point for display speed
fclose(fid);

% remove all points behind image plane (approximation
idx = velo(:,1)<5;
velo(idx,:) = [];

% project to image plane (exclude luminance)
velo_img = project(velo(:,1:3),P_velo_to_img);

% plot points
cols = jet;
for i=1:size(velo_img,1)
  col_idx = round(64*5/velo(i,1));
  plot(velo_img(i,1),velo_img(i,2),'o','LineWidth',4,'MarkerSize',1,'Color',cols(col_idx,:));
end