Make Excel plots with properly scaled axes

Many analytical operations on graphs require that the axes be equally scaled. Measuring the slope of a line on a plot, for example,

requires that the value of the plotted unit be the same on both $x$ abd $Y$ axes $($or a scale factor must at least be known$).$ For

example, the plot of the values listed below should creat a line with a $1$:$1$ slope, or $45$ :

Here is the plot as generated by Excel witrh no adjustment to default parameters.

it using default values

You can see that the line joining the data points does not plot at $45.$ This is because the length of $1$ unit in the $x$ direction is not

equal to the length in the $Y$ direction. By manipulating the Height:Length ratio of the plot I can correct this $-$ approximately.

Now $1$ unit in $x$ is approximately the same length as $1$ unit in $Y.$ There is no way to do this automatically in Excel. You

have to do this manually, and it's very difficult to set the axes to equal unit length except by eye.

Now, however, you can measure the angle of a plotted line and get a meaningful result.

Example$/$Hint: You have to do this to get the correct value for the angle $$ in the Mohr$-$Coloumb failure line.