Showing x,y coordinates of a line

[Smylegirl]

Hi,
I have a graph of some data points and I was pretty sure that I should be
able to run my mouse along the line and wherever I stopped it would show me
the x,y coordinates. But instead I just get (series 1, 10) or something as
unhelpful as that depending on there I am on the line.
I really need this data for a chemistry lab I am doing and I would
appreciate any help possible.
Thank you.

 

[Bernard Liengme]

As a retired chemistry prof I cannot think why you would want to do this. I
think you need to find the equation of the line and compute y for some given
x, or x for some given y. Please tell us more about the project.
best wishes

 

[Jon Peltier]

What version of Excel? What chart type? If I make an XY chart (the only
chart type you should make in chemistry class) in Excel 2003, I get the
series name as well as the (x,y) coordinates when I mouse over the points.

- Jon

 

[Del Cotter]

I have a graph of some data points and I was pretty sure that I should be
able to run my mouse along the line and wherever I stopped it would show me
the x,y coordinates. But instead I just get (series 1, 10) or something as
unhelpful as that depending on there I am on the line.

You're using the "Line" chart type, in which your "x coordinates" are
just being strung out in a row like bottles on a shelf. You would have
got into difficulties if you used that as your graphical display of your
lab results. Try changing the chart type to "XY (Scatter)", and trying
again. Your mouse should report something like "Series 1 (3,10)" instead
of "Series 1 Value: 10)", which is what you get with the line chart. The
chart will now show the lab results in their proper proportions.

I really need this data for a chemistry lab I am doing and I would
appreciate any help possible.

Now the bad news. All you'll get with this solution I propose is the
same data values you typed in, when you hover over the data points. You
won't get interpolated values by hovering over the connecting lines. For
that you should, as Bernard says, use the spreadsheet cells and some
arithmetic to calculate a model of how you think the chemical system is
behaving. Using the model, you can then "predict" what y should be for
each value of x.

Or you could just print the graph out on paper and do what we old people
used to do before they had computers, and use a ruler and pencil to draw
the lines and find the values

 

[smylegirl]

We created a buret correction graph for titration lab and then we titrated a
solution. Now we are trying to figure out the actual amounts dispensed to
figure out the precentage of the unknown weak acid. I have the buret
correction graph and I need to use the actual correction amounts when doing
the equations to figure the precentages. The reason i wanted the x,y
coordinates was because our graph has the data points at 10, 20, 30 mL and so
for forth but the actual amounts that were needed for the titration were not
those exact amounts. So I need to know exactly how much to use for the
correction amount at the point of the line that corresponds to the amount
that we used for each titration. If I brake the graph up into sections I can
use the equation of each slope (the line from 0-10, 0-20, etc.) but it would
just be a lot nicer to have the computer do it for me so then I could plug
the numbers into the equation that I need. I am pretty sure I have seen it
done but I can't seem to get it to work for me.
I hope that makes sense.
Thanks for any thoughts you might have on this dilema!
Crystal

 

[smylegirl]

yes I am using an xy graph and I get the series name but all I get are the
main data points that I typed into my list that I used to make the graph
instead of the the coodinates at any point where I hover my cursor which is
what I am trying to get. According to another replie I may be trying to get
something I can't have...not quite sure, though I know I have seen it work
before I just don't remember how or in what context. For example instead of
just getting (10, 0.0128) I want to be able to hover my cursor at the actual
amount I used and get the coordinates that correspond to that like (7.35,
0.135).
Thanks for your response,
Crystal

 

[smylegirl]

Del,
Ok I was using the xy scattor graph connected with a line and yes all it
gives me are the main data points I put in. I have no idea how to do the
second part that you mentioned about using arthimatic to create a model and
entering that into the spreadsheet data so I'll probably end up isolating the
chunk of the graph that fits the correction volume I need, getting the
equation of the line and work from there with pen and calculator. I don't
mind doing it that way, just thought it would nice to be able to just hold my
mouse where I need it, get a number and plug it into the equation. I guess
these lovely technological devices have their limits!
Thanks for your response.
Crystal

 

[Bernard Liengme]

For the calibration x is the 'reading' and y is the 'actual' amount
dispensed by the buret.
Why not fit the data to a polynomial in the form y=ax^3+bx^2+cX+d (I would
expect a cubic would do) See my website for using LINEST to get a,b,c,d:
http://people.stfx.ca/bliengme/ExcelTips/Polynomial.htm
Then put in the x value and find the y for the titration.
Do all this with a spreadsheet
best wishes

 

[Jon Peltier]

You only get the data points you entered, The line connects adjacent points
but has no intrinsic values to display. For that you'd have to do some kind
of interpolation or curve fitting, and Bernard first suggested.

- Jon

 

[smylegirl]

Thank you for your response and the links. Unfortuately the math is a little
beyond on current grasp and so while I tried to follow the directions i got a
little lost and ended with numbers I have no idea how to use, so i have no
way of knowing if they are even close to being right. I have placed the
links in my favorites though and i plan on spending more time with this to
see if i can make sense of it for this use. I am sure you are on the right
track because one of my fellow students said something about some cubic
formula and did something on his calculator last night just giving me a hard
time but alas i had no idea what he was talking about either. Love the
chemisty, get the concepts, struggle with the math, especially anything
beyond the last level of precalc that I took too many years ago. I am saying
this because I can't say that you solved my problem exactly but maybe given
some more and study I might be able to use the info you sent so I appreciate
your time.

Thanks again,
crystal

 

[Del Cotter]

Crystal

I have no idea how to do the second part that you mentioned about using
arthimatic to create a model and entering that into the spreadsheet
data so I'll probably end up isolating the chunk of the graph that fits
the correction volume I need, getting the equation of the line and work
from there with pen and calculator.

That's a kind of model, just a local one restricted to the area you're
interested in By using the spreadsheet I just meant using the
formulas in cells the way you would punch numbers into your calculator.
I miss my old calculator, but since it died I never bought a
replacement. I just start up Excel instead and doodle as if it were a
pen and paper with a calculator built in.

 

[smylegirl]

ah ok! Thank you for your help on this. I will work on it and see how it
goes. Calculators aren't too expensive if you look on e-bay! I wouldn't be
without my Ti-89, though I confese I don't know probably a 1/2 of what it can
do.
Thanks again, crystal

 

[smylegirl]

yes I guess that is my answer, though certainly not the one I was hoping for!
Oh well I guess it's back to the pen and paper for me since I really don't
know if I'll be able to figure out the interpolation enough to do it
correctly and show my lab partner before it's due! Time will tell I guess.
At least I know it's not just some little radio box I am not clicking or
something simple like that. Thanks so much for your help on this.
Crystal