How to show the negative value on the graph?

Hi everyone, I want to show all the values into the graph including positive value and negative value. This is the expected outcome:

However, I could not display the negative value below 0 at the y-axis, I only can display the positive value only which above 0.

This is the value that I wanted to insert into the graph from the txt file:

Anyone can help me to solve the problem? Thanks in advance.

This is the code that I am using:

semilogy(lai2(:,1),lai2(:,2),'-b')

[Stephen23]

"Anyone can help me to solve the problem?"

Errr... don't use semilogy.

What do you expect negative logarithms to represent?

[KIEN WEI LAI]

I want to show the result as the expected result from the diagram. However, I could not display the negative algorithm.

Answer 1

[Sindar]

If you want to plot both positive and negative data on a log scale, your best bet is to check out symlog: https://www.mathworks.com/matlabcentral/fileexchange/57902-symlog

(It answers a question you seem to be ignoring: what to do with something like -1.00E-01)

However, that doesn't actually seem to be your goal, since your Line #10 (value -3.48E-00) is plotted at -3.48, not -log(3.48) or something like that. And your tick marks are evenly spaced. Your "expected outcome" plot is not on a log scale. Just use plot:

plot(lai2(:,1),lai2(:,2),'-b')