Why the resolution of the plot is bad when I plot longer data?

The m-file 'procKM_tide.m' reads data file 'KM_tde.xlsx' and plot tidal data. I can't understand why the output figure shown on screen and png file present bad resolution. If I plot shorter duration of data, say 2022/12/1 ~ 2023/2/10, the resolution is OK! Why? Any solution?

Answer 1

[Mathieu NOE]

Hello

your line is probably too thick

so change this parameter in this line

plot(tj2,zl,'b-','linewidth',1);%,'markersize',0.5);

I think linewidth value 0.5 to 1 is the optimal range

no need to increase the 300 DPI resolution , it's enough for what we do here

[Ihuan LEE]

Thank you for your answer. You can see the attachments, *1.png is during 2022/12/1 ~ 2023/2/28, *2.png is during 2022/12/1 ~ 2023/2/20. (just set " dayend=28 or 20" in m-file) Rresolution of *1.png is bad !

[Mathieu NOE]

IMHO the resolution seems good , but if you want a better picture you can try with a higher DPI

have you tried for example with 600 or 1000 DPI ?