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Re: Calculating distances between multiple points along a line

Posted by Michael Schmid on Jun 19, 2017; 2:49pm
URL: http://imagej.273.s1.nabble.com/Calculating-distances-between-multiple-points-along-a-line-tp5018921p5018926.html

Hi Adrián,

ImageJ has a tool for extracting data from line graphs:
Analyze>Tools>Analyze Line Graph

https://imagej.nih.gov/ij/docs/guide/146-30.html#toc-Subsubsection-30.14.3

In my experience, it works best if you remove all axes etc. or put a
rectangle around the data, well inside of the axes; it also helps to
apply a threshold to the image (needed especially for plots that come
from jpg-compressed figures like often seen in PDFs).
Unfortunately, it does not accept the axis calibration with offset as
you can set with Image>Adjust>Coordinates; and it has a bug that
reverses the x axis in some cases (possibly related to y axis is
calibration with y ascending in upwards direction.)

[Concerning the point raised by Herbie - I consider it perfectly
legitimate to extract data from other's work for some purposes, e.g. as
a review of a manuscript for consistency checks, for a review article
where you plot several sets of data that you can't get directly from the
authors into one plot (with proper citations, etc. Of course, the
purpose of this tool is NOT to steal data to present them as the own work!]

Michael
________________________________________________________________
On 19/06/2017 15:29, Adrián Villalba wrote:

> Dear all,
>
> I have a graph (line graph) and i want to know he exact at the y-axis of
> all the points of the graph. I think of tracing manually a line over the
> line-graph. Then trace another line among the basal line of the x-axis (the
> zero in the y-axis) and then calculate the distance (in any unit, it does
> not matter) between each point of the graph line and its parallel to the
> basal line. It would give me the proportionality respect a reference point
> to know each value of the graph line.
>
> The fact is that when i try to do it on ImageJ, i can only do it manually
> (which means a huge amount of time) do you know if there is any choice/tool
> to perform this calculation along the line-graph?

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