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I was wondering, if, in whatever the newest version of ios, numbers, and/or pages, it is possible to force a trendline through a point on a 2D scatter graph (e.g. the origin (0,0)). I was hoping to not have to buy excel just because one teacher wants this specific thing.

Edit: Here is a list of what my teacher requires me to do (its a college biology class):

1) Show numbers to 1-2 spaces past decimal point.

2) Adjust document page setup so all cells of a table appear on the same page.

3) Always plot the independent variable on the X-axis

4) Always plot the dependant variable on the Y-axis

5) Label both axes with the quantity being measured

6) Except where data is processed as a ratio, the numbers must be associated with specific units. Include on the graph axes or in table cells.

7) Number the axes appropriately at regular intervals

8) Show the equation for the trend line.

9) There must be a good title [insert long explanation here]

10) If there is more than a single data set plotted on a graph, distinguish between them via shapes or colours.

11) Adjust the scales of the X- and Y- axes so that: a) All data points fit on the graph b) Both axes are reasonably close to the same length. c) You are using a reasonable portion of the overall page of graph paper.

12) a) For a standard curve, from which values will be extrapolated (which I am doing in this case), draw a best-fit straight line. In a linear graph the line is typically forced to go through the origin. 1 b) For graphs that aren't standard curves, if the points seem to line up in a straight line or if the relationship is known to be linear, dea a best-fit straight line (which may or may not go through the origin)

c)....(not applicable to my question)

d)....(not applicable to my question)

e) Smoothing curves for aesthetic reasons "MUST" be avoided.

f) Adding portions of lines on graphs for which there is no data must be avoided.

  • What does your teacher want? I think Numbers does most everything that can be done in excel. – jmh Sep 11 at 22:06
  • She wants the trend line (at least this time) to go through the origin, a feature in neither open office 3, open office 4.1.6, or pages / numbers (current as of sept 11, 2019) – Celi Sep 11 at 22:27
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The trendlines are based on the data and can't be forced thru any points. What you could do is have the app print out the equation for the trendline and plugin 0 to see what new trendline looks like. You can then adjust the coefficients so that you have a new trendline thru 0.0. This may not be a good representation for the trendline.

Another possibility is to add several pairs of 0.0,0.0 to the row and column you are plotting. Start with just 2 or 3 pairs and see how that affects the trendline. Depending on your trendline, you may need more pairs. this will weight that part of trendline more than other parts and will cause a shift in the line.

It should be noted that the trendline you enforce will probably not represent the data very well. If the value at 0.0 is actually 245, while the other values you have are in the range of 200-250, for example, forcing it to zero at zero is a bad idea. Adding data points is also a bad idea because you inputting data that doesn't exist grossly changes your data set.

The trendline is a representation of the data in a relatively simple manner. Changing it makes it no longer representative of the data. If you suspect your data at 0.0 should be 0.0, then this is probably a method to determine that.

  • Thank you for your answer. It helps a bit. I was thinking about the accuracy issue too, but my teacher specified "the trend line or line of best fit must go through the origin."... (and I need to show the equation for the trend line). – Celi Sep 11 at 22:12
  • is this from a data set, measurements you made, or data downloaded from elsewhere? Maybe she wants you to pick an equation type that will go thru 0. You can choose different types of trendlines. Like linear, polynomial, Exponential, etc.. If your data looks linear, use linear trendline. If the data set looks curved, use polynomial. May be one of these will go thru 0.0... – jmh Sep 11 at 23:16
  • It is from a data set I made in lab, and she specified linear. – Celi Sep 11 at 23:20
  • Sounds like she wanted you to get the accuracy such that the trendline will go thru 0.0. And the precision as well. I should have asked you this first. If your trendline for your data doesn't go thru 0.0, you should make more measurements carefully. Adding more measurements will improve your accuracy and decrease the uncertainities. – jmh Sep 11 at 23:35
  • I did not know that and I will keep it in mind for future labs, thank you. Sadly, this time I was limited by the amount of solution. – Celi Sep 12 at 5:07

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