Matlab draws graphs with matrices

Article directory

Part.I Introduction
Part.II Drawing with Matrix

Part.I Introduction

This article summarizes several ways to draw graphs with matrices in Matlab.

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Chapter.I Preliminary knowledge

关于 *.mat文訳

*.matThe file is the standard format for matlab data storage. It is a standard binary file and can also be saved and loaded in ASCII code. When opened in MATLAB, the display is similar to a single-line EXCEL table. The syntax for loading and storing mat files is:

// 加载 mat 文件
load('C:\Users\Lenovo 110\Desktop\Clustering-master\data\toy_clustering.mat')
// 保存 mat 矩阵
// 第一个参数是文件路径，后面的参数矩阵名字，类似于load
// 当只有第一个参数的时候，会把工作空间所有的矩阵都存在一个文件中
save('C:\Users\Lenovo 110\Desktop\Clustering-master\data\mydata.mat','r2','r3')

Chap.II Overview

There are several main ways to use matrices to draw pictures:

// 方式 1  --  常用
imshow(SST);		// imshow(SST,[]);
// 方式 2
F1=mapminmax(SST); %F1 ∈[-1,1]
F1=F1.*0.5+0.5; %F1 ∈[0,1]
// 方式 3  --  常用
imagesc(SST);
// 方式 4
contourf(SST,'LineStyle','none');
colormap(jet); colorbar
// 方式 5
pcolor(SST);

Chapter III Miscellaneous Notes

Here are some miscellaneous notes

R = corrcoef(cov1);		  		// 求协方差矩阵的相关系数矩阵

Part.II Drawing with Matrix

Chap.I The process of exploration

1. First load a matrix:
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You can see that there are nan and normal data in the matrix. In order to get an overview, I put these data into Excel, and then zoomed out as shown below:

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Then let’s introduce the characteristics of the matrix:

[a,b]=size(m);
num=a*b-numel(find(isnan(a)));                  %矩阵中除了nan外所有元素的个数
m1=reshape(m,a*b,1);      %搞成一个列向量
max1=max(m1);             %计算最大值
min1=min(m1);             %计算最小值
mean1=nanmean(m1);        %计算除nan之外的均值
mode1=mode(m1);           %除了nan 返回值最小的那个众数
med1=nanmedian(m1);       %求除了nan的中位数
// -----------------------------------------
217x217
max1=20.21
min1=1.22
med1=7.055

Now that I have a general understanding of what the data looks like, let's start trying to draw a graph.

code	image
–
`imshow(SST);`
`imshow(SST,[]);`
`F1=mapminmax(SST); %F1 ∈[-1,1]` `F1=F1.*0.5+0.5; %F1 ∈[0,1]` `% [y,ps] = mapminmax(SST);` `% ps.ymin = 0;` `% [y,ps] = mapminmax(SST,ps); %这三行与上面两行异曲同工`
`imagesc(SST);`
`contourf(SST,'LineStyle','none');colormap(jet);colorbar`
`pcolor(SST);`
`A=[0.8 0.1 0.5` `0.2 0.4 0.7` `0.5 0.3 0.6];` `imagesc(A);` `colormap jet` `colorbar;`
`A=[0.8 0.1 0.5` `0.2 0.4 0.7` `0.5 0.3 0.6];` `imagesc(A);` `colorbar` `caxis([0 1])` `[M, N] = size(A);` `set(gca, 'XTick', 1:M,'XTickLabel', {'0','1','2'})%X坐标轴刻度数据点位置、字符` `set(gca, 'YTick', 1:N, 'YTickLabel', {'0','1','2'})` `loc = get(xlabel(''), 'position');` `text(loc(1), loc(2), loc(3), 'Predicted label', 'HorizontalAlignment','center');` `set(gca, 'XAxisLocation', 'top')` `ylabel('True label')` `title('Confusion matrix')`

Currently, I only know these types, and the sixth one is the most useful;imshow() can only display grayscales between [0,1], greater than 1 Displayed in white; imagesc() displays the image in color, with no value restrictions; colormap() displays the image in color. For colormap, please refer to the following article: a>

https://blog.csdn.net/weixin_42943114/article/details/81811556

Chap.II Draw professional drawings

Let’s create a more professional graph below. The data used is still the matrix above217x217.
The code is as follows:

X=117:0.0416666666666:126;
Y=33:0.0416666666666:42;
x0=2*24:2*24:217; % 每隔两度标一下
y0=2*24:2*24:217;
x=119:2:126;  %标注用的
y=35:2:42;    %标注用的
x1=sprintfc('%g',x);%转成字符串数组
y1=sprintfc('%g',y);%转成字符串数组
n=size(x1,2);
for i=1:n
    x1{
    
    1,i}=[x1{
    
    1,i},'°E'];
    y1{
    
    1,i}=[y1{
    
    1,i},'°N'];
end

figure1 = figure;
ax2=axes('Parent',figure1);;%有子图时，ax2=subplot(2,3,2);
contourf(SST1,'LineStyle','none')
colormap(jet);
set(gca,'XTick',x0,'XTicklabel',x1);   %设置x,y轴
set(gca,'YTick',y0,'YTicklabel',y1);
set(gca,'FontName','Times New Roman'); %更改字体为罗马
xlabel('(a)  SST');
set(ax2,'XAxisLocation','top');%把x坐标轴搞到上面去
h=colorbar;
set(get(h,'Title'),'string','K'); %给colorbar加上单位

result:
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Chapter III matrix to tiff

Still using the matrix in 2

GeoRef = georasterref('Rastersize',size(SST'),'Latlim',[double(min(Lat)),double(max(Lat))],'Lonlim',[double(min(Lon)),double(max(Lon))]);
%数据的写出
% data = flipud(SST');
SST_Tif = ['C:\Users\hp\Documents\MATLAB\','A20160922016121_01.tif'];
geotiffwrite(SST_Tif,flipud(SST'),GeoRef)

Pay attention to the front and back of the picture. The following picture is from the front:

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