Adding Points using API with DateTime Axis and DBNull values

[User (Legacy)]

Hi,

I am using ChartFX for VS .NET 2005 to plot multiple series against a 

DateTime axis.

I have been using an ADO .NET DataTable successfully to plot a single series 

of GalleryType=Step based on a column with no DBNull values, and now I need 

to display multiple series, each of which has many DBNull values.

I can't seem to get even 1 series of data with some DBNull values to plot 

against a DateTime axis when the data has null values, when I use data 

binding instead of the ChartFX API to add 1 point at a time.

Questions:

1. How can I add a point to a ChartFX chart using the API when the X-Axis is 

a DateTime axis?

chart1.Data[seriesNumber, pointNumber] seems to make no reference to a 

DateTime X-Axis.

2. What's the best way to plot 3 or 4 series from an ADO .NET datatable 

whose columns have some DBNull values?

If I use DataBinding, what is the easiest way to hide the DBNull points?  Is 

it better in this case to loop through the points and add them one at a time 

using the API?

3. What else should I know about trying to plot DBNull values, esp. against 

a DateTime X-Axis, using ChartFX for VS .NET 2005?

Thank you very much,

Brook Hunter

[Software FX]

> 1. How can I add a point to a ChartFX chart using the API when the X-Axis 

> is a DateTime axis?

First of all, it is important to distinguish between two possible uses for 

the date (x-axis) values:

a) If the chart type is a line chart or any other type that supports X/Y 

coordinates, the X-Axis is independent of the data itself and the points are 

plotted at their position according to the X-Value. This allows for multiple 

series having different date x-values.

 If the chart type does not support X-Values, such as Bar, the dates are 

used as "data-driven labels", this means the dates do not affect the 

position of the bars but they only affect the labeling of the X-Axis, in 

this case, only the first series´ X-Values (or shared X-Values) are used, 

therefore you can not combine two series with different sets of x-values.

If there is only one date column in your dataset, both scenarios can be 

achieved (shared X-Values).

To assign X-Values using the API you can use:

chart.Data.X[i,j]

> 2. What´s the best way to plot 3 or 4 series from an ADO .NET datatable 

> whose columns have some DBNull values?

This depends on how do you want to interpret null values. By default Null 

values are translated into "hidden" points, which means that the space 

allotted for this point will be left blank, in a connected chart type, such 

as line, this will generate a break in the line (you can bypass this break 

by using DataValues.InterpolateHidden, see docs for details). Your data 

would look like this:

Date         Series1         Series2

1/1/2001    30                40

1/3/2001    20

1/4/2001                        45

1/5/2001                        70

1/6/2001    50                60

If you are doing a Line chart (or a chart supporting X-Values) you may 

decide to strip these null values from your dataset so that Chart FX  only 

receives the actual values (no nulls), since the dates dictate the position 

of each point, you will need a separate set of dates for each series, your 

data will end up looking like this (for the same data):

Date1        Series1        Date2        Series2

1/1/2001    30            1/1/2001          40

1/3/2001    20            1/4/2001          45

1/6/2001    50            1/5/2001          70

null            null            1/6/2001          60

Notice that using this approach, all null values (if any) end up at the end 

of the dataset.

> 3. What else should I know about trying to plot DBNull values, esp. 

> against a DateTime X-Axis, using ChartFX for VS .NET 2005?

The information above should cover this one.

-- 

Francisco Padron

www.chartfx.com