# How can I interpret this scatterplot?

Please help me to interpret this graph in terms of correlation type. Which type involves two vectors in directions observed below (see graph screenshot)? Thanks in advance.

• Check the updated graph. For now I'm saying that y1 and y2 content is directly correlated to the lower content of X. when X is lower, the y1 content decrease while the y2 increase. – Apopei Andrei Ionut Feb 21 '14 at 13:51
• What are y1 and y2 then? Are they separate variables? And what are the dots? Do their coordinates represent observations of two different variables or three? If three, how can one tell the difference? And why do the vectors pass outside the observations rather than through them? – Nick Stauner Feb 21 '14 at 13:56
• y1/(y1+y2) (which is equivalent to that representation y1 and y2) - are to variables on the y-axis, an the third on x-axis. Dots represents the projected values of y1/(y1+y2) vs x. The vectors represent the trend. – Apopei Andrei Ionut Feb 22 '14 at 17:19
• If your y axis is the ratio of two dependent variables, you may wish to also consider graphing them separately, or using other methods to look at the relationship between all three. The change in variation of the data with x may indicate that ONE of the y values is correlated with x, and it becomes more dominant in the total and the ratio at higher x values. But you can't say for sure just based on this plot. – AmeliaBR Feb 23 '14 at 21:10

Assuming the dots are your observations, the vectors seem to express upper and lower bounds on the range of $y$ as a function of $x$. The correlation appears weakly negative at a glance, but I wouldn't really trust my eyeballs to estimate Pearson's $r$. What does seem clear enough is that $y$ exhibits across $x$. Wikipedia's Consequences section may be of further interest to you. See also for comparison Wikipedia's plot with random data showing heteroscedasticity: