# Input as an ordered pair instead of as a matrix [closed]

when I input pp = {{2.0, 10}, {4, 19}, {6, 31}, {8, 40}, {10, 51}, {12, 59}, {14, 70}} and press enter I get a matrix output. I want it as an ordered pair to find the best fit line, using Fit[pp,{1,x}x], which it does but when I plot the line and the try to plot the points mathematica interprets my data as a matrix and does not plot it. Why? Before I did this same method and was able to plot both the points and the line on the same graph. Please help anyone.

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## closed as off-topic by rm -rf♦Sep 16 '13 at 14:10

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Have a look at the docs for ListPlot. For example: ListPlot[pp]. –  bill s Sep 16 '13 at 3:29
Maybe Plot[Evaluate@Fit[#, {1, x}, x], {x, 0, 14}, Epilog -> {Red, PointSize[Large], Point[#]}, AxesOrigin -> {0, 0}] &@pp –  TomD Sep 16 '13 at 14:19

It sounds like you may be having an issue trying to plot the discrete data, pp with a continuous function, i.e. what is returned from Fit. You may consider picking a different title for your post because in Mathematica an ordered pair is always interpreted as a matrix.

First define the data set and extract the max and min x-values to make plotting easier:

pp = {{2.0, 10}, {4, 19}, {6, 31}, {8, 40}, {10, 51}, {12, 59}, {14, 70}};
x0 = Min[pp[[All, 1]]];
xf = Max[pp[[All, 1]]];


Next call Fit on your data to generate a linear fit. Note that in this way we are forced to plot line using the dummy variable x:

line = Fit[pp, {1, x}, x];


Plot the discrete data using ListPlot and the continuous function using Plot. Store the outputs in p1 and p2 respectively such that we can use Show to display them together:

p1 = ListPlot[pp];
p2 = Plot[line, {x, x0, xf}];
Show[p1, p2]


Which produces a plot of your data along with the linear fit.

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Thank you. This is what I get: –  Ali Bautista Sep 16 '13 at 3:51
Show::gcomb: Could not combine the graphics objects in Show[Listplot((7x2 matrix)).... –  Ali Bautista Sep 16 '13 at 3:56
I understand that mathematica interprets my data as a matrix and not as a pair of points to plot. That is my problem. –  Ali Bautista Sep 16 '13 at 3:56
When I input pp = {{2.0, 10}, {4, 19}, {6, 31}, {8, 40}, {10, 51}, {12, 59}, {14, 70}} and press enter a 7x2 matrix form is returned. That is what I do not want. –  Ali Bautista Sep 16 '13 at 4:04
Thank you. You were right, my mistake was a typo. Thank you. –  Ali Bautista Sep 16 '13 at 4:10

f = Fit[pp, {1, x}, x]

If you need model data use LinearModelFit