The first step of Time Series Analysis is to analyze time series data visually. The line graph is the basic tool.
Very easy, but this graph indicates variance, tendency and abnormality. Even if we do not know appropriate mathematical aproach, this visual approach is effective.
X-axis is time series and Y-axis is quantity. The stratified sampling is better.
Check points to read line plot are "Increasing or decreasing?", "Periodical?", "Partial movement?" , "Unusual Value?", "Large difference?", "Different values from set up?".
Software that makes many line-graphs efficiently is a strong tool. That is the reason why I explain programming and macro in this site.
NEXT Heat Map