Need to plot speed heatmap

I have an excel sheet having data of time, distance(postmile) and speed in three columns

I have to plot 2d high resolution heatmap of speed as follows; time in x-axis, distance(postmile) in y axis and speed in z axis with color. Can anyone help me to provide matlab code for this

Answer 1

[Anurag Ojha]

Hi, Laxmi

To draw a heatmap for 3 variables you can simply turn your data into an image, for example, a 1000x1000 image. Then display the image using “imshow” or “image” and then use “colormap” and “colorbar”.

%Taken 3 variables in your case time,displacement and speed  

x = 1:100; 
y = 2:102; 
z = 50:150; 

% Doing this so that any unassigned values 
% (like you don't have every single possible x and y value in your data) will be 
% set to the mean value of what data you do have. 

minx = min(x); 
maxx = max(x); 
miny = min(y); 
maxy = max(y); 
meanValue = mean(z); 
heatMapImage = meanValue  * ones(1000, 1000); 

% Here creating the heatmap and storing it in heatMapImage array 

for k = 1 : length(x) 
  column = round( (x(k) - minx) * 100 / (maxx-minx) ) + 1; 
  row = round( (y(k) - miny) * 100 / (maxy-miny) ) + 1; 
  heatMapImage(row, column) = z(k); 
end 

%Convert the array to image using imshow and adding colorbar 

imshow(heatMapImage, []); 
colormap('hot'); 
colorbar; 

To further explore you can refer to below links:

• Colormap
• Create Heatmap
• imshow
• Max and min

Hope it helps!

[Laxmi Bhatta]

Hi there

I have attached table, I am new to MATLAB, if you could make code for plotting one heatmap having time in x (column3) axis, postmile in y axis (column 2) and speed (column 4) in z axis would be appreciated.

Thanks