Standard Additions plotting in excel

[Divine]

Homework Statement

I have a set of values from a laboratory work (standard Additions practical), which I am required to plot. I am finding difficulties in plotting the values in excel because the horizontal axis must have some negative integers.

Homework Equations

The Attempt at a Solution

 

[Borek]

No idea what your problem is, last time I used it, Excel supported negative numbers.

 

[phinds]

Have to agree w/ Borek. Can't see what your problem is

 

[Divine]

Standard Additions

Homework Statement

I have a set of values from a laboratory work (standard Additions practical), which I am required to plot. I am finding difficulties in plotting the values in excel because the horizontal axis must have some negative integers.

Homework Equations

The Attempt at a Solution

Hello Borek,
My problem is that I don't know how to make such plots in excel. As you might be aware, there is the need to extrapolate the calibration line backwards so as to obtain a negative value on the X-axis. This is what I cannot do and will appreciate it if someone could help me.
The example given below is of no help as it looks nothing like a standard additions plot.

Thanks.

 

[Yanick]

Have you plotted your data and fit a line already and don't know how to extrapolate or do you not know how to plot and fit data?