Archive for the 'Formulas' Category



Correction to “elapsed time string” formula

Saturday 9 November 2019 @ 11:54 pm

My web site has a page for commonly used formulas.  Many have been there for years.  Formula page 9 has two versions of a formula that will convert a number of seconds into an elapsed time string. The long version has days, hours, minutes and seconds.  The shorter version is just hours and minutes.

I was using the short version in a customer’s report and we noticed that the minutes value was sometimes off by one.  After some testing we found that if the remaining seconds were between 30 and 60 the formula would always round down because the formula used a Truncate() function. The Truncate() works correctly in the long version of the formula, because you truncate down to the whole minutes and then display any remaining seconds. But since the shorter version doesn’t display seconds it is more accurate to Round () the seconds to the nearest minute.  So I have updated the short version formula on my site to use the Round () function for minutes.

So those of you who have used that formula should update your reports by changing the last Truncate to a Round, or just taking the updated formula from page 9.




No column headings on the last page (v2.0)

Tuesday 29 October 2019 @ 7:29 pm

Last month I wrote an article about suppressing the page header on the last page when there are no details. This is handy if your last page is a subreport, a chart or a cross-tab. After my newsletter went out one of my readers shared her approach to the same problem. She uses the group header of a dummy group, and sets it to “repeat” on each page.

Any time you have a Group Header you can set it to repeat on each page. One feature of  a repeating GH is that it won’t appear on the last page of a group, unless that page has at least one detail record.  I wrote about that behavior in another article long ago.  So the only trick is to create a primary group that includes every record in the report. Then you set this group header to repeat on each page and it behaves just like a page header, with the exception of not printing on the last page.

So how do you create a group that includes all the records in the report? You group on a value that doesn’t change.  If you have a DB field like “company” that doesn’t change you can use it.  But you can always create a formula that isn’t tied to any data fields.  My favorite dummy group formula is:

WhileReadingRecords;
"All"

The word “All” can be any value. Just keep in mind it will appear as the overall node of the group tree so you might want it to make some sense. The WhileReadingRecords function allows the report to see this static value as a recurring value, which makes it eligible for grouping.

Once you create the formula you use it as Group 1 in the report and then go into Group Options and check “Repeat Group Header on each new page”.  If you put your column headings in this Group Header they will appear on every page, but won’t appear on the last page (unless there are details printing on that page).

And thanks to Tina Nordyke, the DBA for Advocates for Basic Legal Equality, Inc for suggesting this method.




Literal values that include quotes

Saturday 26 October 2019 @ 12:25 am

I was recently working on a formula that had the crystal syntax for “is one of”.  It looked something like this:

{LastName} in [ "Smith","Jones","Thompson","Rutledge","Harris" ]

Each value goes in quotes (single or double). You separate the values with a comma and you put square brackets around the list. So I was surprised today when I saw that the formula was actually like this:

{LastName} in [ "Smith""Jones","Thompson","Rutledge","Harris" ]

Notice the comma missing between the first two values.  The report had been running for months without error messages which I didn’t understand, so I started testing.  My experiments pointed me to a syntax rule that I had read about but never used. It is for when your formula includes a literal string that you surround with double quotes, and when the literal string itself contains double quotes.  Crystal would assume the first quote is the ‘open’ and the second one is the close, even when you want the second one to be part of the visible output.   One solution is to use two consecutive double quotes within the literal. Whenever Crystal finds two consecutive double quotes within a literal surrounded by a pair of double quotes, Crystal will interpret the consecutive quotes as one literal quote and not as a closing quote.  This is much easier to explain with an example.  So if I wanted a formula to output this string:

The syntax for "is one of" uses brackets

I could write it like this inside the Crystal formula:

"The syntax for ""is one of"" uses square brackets"

The formula engine would only display one of the two consecutive double quotes in each pair.  That explains why my formula with the missing comma doesn’t generate an error.  Crystal treated the consecutive double quotes as a single literal and then combined the first two elements in the list as being the single value:

Smith"Jones

There was no error message, but the results would not have been correct.

BTW, the same principle applies to single quotes. If you put two consecutive single quotes in a string surrounded by single quotes, Crystal will ignore the first and treat the second as a literal quote.

The reason I didn’t think of this right away is that I have never used consecutive quotes in a formula. If I have a string that needs to contain single quotes I surround it with double quotes. And if the string needs to contain double quotes I surround it with single quotes. In the rare case that a string needs both I would split it into separate pieces and combine them. I find that using consecutive quote pairs makes the formula harder to follow.




Suppress column headings when there are no details on the last page

Sunday 22 September 2019 @ 10:38 pm

Sometimes there are details printing on the last page and sometimes the last page is just the Group or Report Footer.  You may not want column headings on the last page if there are no details.  I have seen and tried several methods to accomplish this but not all are reliable. For instance using “OnLastRecord” as a suppress condition will work most of the time, but will also suppress the headers when the last page still contains exactly one detail record. I have found the approach below to be the most reliable.

First you split the Details band into A and B subsections.  You suppress Details B and use Details A for your visible fields.  Then you create the following formula field and place it in Details B:

WhilePrintingRecords;
BooleanVar Ending := OnLastRecord

Last you use the following formula to suppress the Page Header, or the part of the Page Header with column headings:

WhilePrintingRecords;
BooleanVar Ending

A Boolean variable is False by default.  The variable will only be True once the report has passed the last Detail A, which means that the last record has printed.  If there is a page header after that point it will be suppressed, because the “Ending” variable is now True.




Real rounding vs fake rounding

Sunday 8 September 2019 @ 8:00 pm

Crystal makes it easy to reduce the number of decimals that you display for numeric values. There are two buttons on the toolbar (near the percent sign) and these allow you to either reduce or increase the decimals displayed. When you reduce decimals the remaining digits will either round up or down based on the digits no longer displayed. In other words, if you are showing 75.28 and you click the button to reduce the decimals displayed by one, the value will display as 75.3. This is because the hidden 8 causes the value to round up to the next 1/10th.

However, this is deceptive. The underlying value in the report is still 75.28. And if you were to total that column or use that value in a calculation the value used would still be 75.28. This can give unexpected results, because the visible total at the end of the report might not reflect the sum of the visible values that go into that total. For that reason, I call this ‘fake’ rounding. You will find the same type of issue in Excel spreadsheets.

Most of the time, this isn’t an issue. And many people who read financial statements understand ‘rounding errors‘. But there are cases where you need ‘real’ rounding. Real Rounding requires writing a formula that uses the Round() function. For instance, if you have to apply a tax rate to a purchase and the calculated tax amount.  You could use a formula like this:

{Sales.Charge} * {Sales.TaxRate}

But if the tax value has more than two decimals, those extra decimals aren’t real.  Most transactions have to be rounded to the nearest penny. In these cases you would need a formula like this:

Round ( {Sales.Charge} * {Sales.TaxRate} , 2 )

This rounds the tax to the nearest penny.  If you used the first formula and created a total of the tax values, the total would include all the fictional fractions of a penny.  If everything was displayed with two decimals the total tax would not match the individual tac values, because those would be using fake rounding to display only two decimals.  But if you use the second formula and then create a total of that formula the total should reflect the visible values.  The total calculation is using values that display the same number of digits as the underlying value.




Math tweet splits internet mathematicians

Tuesday 20 August 2019 @ 12:10 pm

One of my colleagues sent me a New York Times article about a math tweet.  The tweet was of a deceptively simple math equation and asked people to calculate the result.  All of the internet mathematicians immediately divided into two camps based on their interpretation of the rules of precedence, which were intentionally ambiguous in the equation. The point of the article (and of my colleagues sharing) was the importance of using parentheses to clarify the order in which things should occur. I often add extra parens, even when the order of precedence wouldn’t require them, just to give myself a visual clue of what is supposed to happen when.

The funny thing about the original article, and an interesting follow-up article, is that experts can still be found on both sides of the divide. That is somewhat surprising given the apparent simplicity of the problem.

And thanks to Zvi Flanders of Huron Consulting for sending me the link.




Calculating the begin and end of Daylight Saving Time

Friday 16 August 2019 @ 11:32 pm

I am not a big fan of Daylight Saving Time (DST). I even hear some states and countries are talking about dropping it (yeah!). But in the meantime there are plenty of reports that need to adjust the time twice a year. This usually happens when the datetime values are stored in Greenwich Mean Time (GMT) and have to be converted to a local time. Then you need to know when DST begins and ends.

The first two formulas below calculate the beginning and ending dates of DST, based on the year of your transaction date. The third formula uses the first two formulas to make the one-hour adjustment. Substitute your GMT date fields into the first and third formula.

//DST Start
DateVar Start:= Date (Year ({@YourDateTimeGMT}) , 3, 15);
DateVar BOM:= Start - Day(Start)+7;
DateVar BOW:= BOM - DayOfWeek(BOM) + 8;
DateAdd('h', 2, BOW);

//DST End
{@DST Start} + 238 ;

//Adjusted DateTime
if {@YourDateTimeGMT} in {@DST Start} to {@DST End}
then DateAdd('h', 5, {@YourDateTimeGMT})
else DateAdd('h', 4, {@YourDateTimeGMT})




When that zero isn’t really a zero

Thursday 8 August 2019 @ 10:24 pm

Last week a customer was really befuddled. He had a formula that said:

if {@field} = 0 then ...

He could see lots of zero values but the formula didn’t work as expected.  He couldn’t figure it out so he sent it to me. The first thing I did was add a few more decimals to see if it was a rounding issue. That didn’t show anything, but the formula still insisted that the value was somehow NOT equal to zero.

So I went into the formula and multiplied the current value by one trillion. Then instead of zeros I started to see some small numbers.  I am not an expert on floating point values or database precision but I have seen this before in reports.  The solution is to round the value in the formula before comparing it to zero. In this case we rounded the value to two decimals like this:

if Round ({field}, 2) = 0 then ....

That made the formula behave as expected.  The odd part is that I have seen the same problem with two other customers in the past week. It could be just a coincidence, but I figured I would mention this and see if this is happening to more people.




Preventing the “division by zero” error

Friday 26 July 2019 @ 9:52 am

Crystal formulas can use 3 different divide operators:

  • Regular divide [ / ]
  • Integer divide [ \ ]
  • Percentage [ % ]

But all of these will fail if you follow the operators with a zero. The report will stop and Crystal will throw the error message “Division by Zero”.  The standard solution is to check and make sure the number you are dividing by is not zero before you do the calculation, something like this:

if {fieldA} = 0
then 0
else {fieldB} / {fieldA}

This way, whenever the bottom of the fraction (denominator) is a zero, the formula will print a zero and NOT try to do the calculation.

But even when customers use this formula pattern I still see the divide by zero error. Some users mistakenly check the top of the fraction (numerator) instead of the bottom (denominator).  Some do it correctly at first, but then change the denominator and forget to change the first line to match.  So I have developed the habit of using Local variables to make things easier. My normal pattern now looks like this:

Local Numbervar n:= {FieldA};//numerator
Local Numbervar d:= {FieldB}; //denominator
if d = 0 then 0 else n/d

This ensures that the value being checked is always the value on the bottom. Some other advantages of this method are:

1) If d is a subtotal or a long expression you only have to enter it in one place.
2) If you have to create a series of similar expressions, like for 12 different months, you can duplicate the first example and you only have to change the values at the top of the formula.




How to make sure you are on the last day of the month

Friday 19 July 2019 @ 9:18 am

Lots of reports require that you compare two different date periods and I often calculate prior date ranges based on the current range. But you have to be careful when the end of your prior period falls in a month with more days the the current period month?

Here is an example. Lets say your current period is in June and your prior period ends 6 months earlier in December. Calculating the Start Date is simple. If your Current Start is 6/1/2019 you can use a simple DateAdd like this:

DateAdd ('m', -6, {@CurrentStartDate})

but if you try a similar formula for the End Date you won’t get the right date. The following formula will return 12/30/2018:

DateAdd ('m', -6, {@CurrentEndDate})

The same issue occurs when your prior period is a year before and your current period ends in February. If he prior year is a Leap Year your prior period end date will be off by one day, ending on the 28th rather than the 29th.

My solution involves adding one day before you do the DateAdd and then subtracting that same day back out again, like this:

DateAdd ('m', -6, {@CurrentEndDate} +1) -1

This works because adding the one day puts on you on the first of the month. This is always a clean calculation when moving forward or backward by months or years. Then once you get to the first of the month in the prior period you subtract one day which always puts you on the last day of the month prior.




Next Posts »» «« Previous Posts
Jeff-Net

Recrystallize Pro

Crystal Reports Server